Rickets
in Nigerian F. Okonofua,
Children: D.S. Gill, 2.0.
A Consequence Alabi,
M. Thomas,
of Calcium
Malnutrition
J.L. Bell, and P. Dandona
Eleven Nigerian children with clinically and radiologically proven rickets were assessed biochemically. The children had low or low normal concentrations of total and corrected calcium, and elevated plasma alkaline phosphatase (ALP) activity, but normal plasma phosphate concentrations. Their serum 25-hydroxyvitamin D (25.OHD) and 1,25-dihydroxyvitamin D (1,25-(OH&D) concentrations were not significantly different from those in controls, but the ratio of 1,25-(OH&D to 25-OHD was significantly greater than that in controls. Parathyroid hormone (PTH) concentrations were greater in rachitic children, and there was a significant correlation between 1,25-(OH),D and PTH concentrations. Osteocalcin concentrations in rachitic children were not significantly different from those in controls, but they were markedly elevated in the three patients with the highest 1,25-(OH),D and PTH concentrations. One child, from whom a sample of bone (from a corrective osteotomy) was available for histological examination, showed markedly thickened osteoid seams, characteristic of rickets. All the rachitic children had a calcium intake of less than 150 mg daily. Treatment of these rachitic children with calcium gluconate (1 g/d) led to clinical, radiological, and biochemical healing of rickets. We conclude that rickets in Nigerian children is not due to vitamin D deficiency, but to a lack of calcium. This observation has implications regarding the pathogenesis, treatment, and prevention of rickets/osteomalacia in Nigeria and possibly other African and tropical countries. Copyright 0 1991 by W.B. Seunders Compeny
R
ICKETS ARE KNOWN to occur in Nigerian children from the lower socioeconomic groups.’ No biochemical data are available hitherto to establish the pathogenesis of this condition in this population. In a previous study, we have demonstrated that the concentrations of 25hydroxyvitamin D (25OHD) in sera of pregnant Nigerian women are greater than those in pregnant white women in the United Kingdom.’ This was true of even purdah-clad Muslim women in Nigeria, who have lower 25OHD concentrations than those who are not in purdah’; yet the children of purdah-clad Muslim women have a tendency to develop rickets, while those of white women in the United Kingdom do not. In contrast, purdahclad women in Saudi Arabia, whose children also have a tendency to develop rickets, have extremely low 25-OHD concentrations, comparable to those observed in Asian women in the United Kingdom.3 In order to explain this paradox, we have now investigated Nigerian children with rickets and age-matched controls. The observations suggest that the development of rickets in Nigerian children is not primarily due to vitamin D deficiency, but rather is associated with diminished calcium intake. PATIENTS,
MATERIAL,
AND METHODS
Ten Nigerian children (seven boys, three girls) with clinically and radiologically proven rickets, and 12 age-matched controls (nine boys, three girls) were included in the study. The controls had no clinical evidence of rickets or other forms of malnutrition. All children were attending outpatient clinics in University College Hospital in Be-Ife, Nigeria, and were not on any form of treatment. The age of the patients ranged between 3 to 5 years. One additional rachitic patient was included in the study: a boy of 9 years who had clinical and radiological rickets and genu valgus deformity (Fig l), since the operation of corrective osteotomy in this patient provided us with a sample of bone for histological analysis. All patients had painful swellings of wrists and/or knees; x-rays of the region confirmed an irregular expansion of the epiphyseal cartilage. The dietary calcium intake of each of these children was 150 mg/d. The phytate intake of these children was high, since their diet consists mainly of cassava with maize, yam, and plantain. The supply of the latter three is seasonal. There was no milk or any other dairy product in their diet. The dietary intake of calcium was calculated from the total amount of cassava, maize, Metabolism, Vol40, No 2 (February), 1991: pp 209-213
yam, and plaintain consumed, and by multiplying this with the calcium content of each of these foods. The control children had a daily intake of calcium greater than 300 mg. Rachitic children were treated with calcium gluconate 1 g/d for between 40 and 230 days, after which they were lost to follow-up. During the follow-up period, their plasma calcium concentration and alkaline phosphatase (ALP) activity was measured. X-rays were taken to demonstrate radiological healing. Serum samples obtained at follow-up were not large enough for vitamin D and parathyroid hormone (PTH) studies. Blood samples were obtained from the children with rickets and the controls after an overnight fast. Five milliliters blood was collected in heparin; plasma was separated. The remainder was collected in plain glass tubes and allowed to clot. Serum was separated and divided into three aliquots. Plasma and serum samples were frozen immediately at -20°C and stored in this state until they were transported in dry ice to The Royal Free Hospital, London. Plasma calcium, phosphate, ALP, total protein, urea, and electrolyte concentrations were measured on a SMAC Technicon Autoanalyzer. 25-OHD was assayed by the method described by Hummer et al,’ while 1,25-hydroxyvitamin D (1,25-(OH),D) was assayed by the method of Reinhardt et al using a 1,25-(OH),D receptor from calf thymus.5 Serum PTH was measured by a radioimmunoassay using an antibody directed against the mid-fragment of the PTH molecule.6 Osteocalcin concentration was measured by a specific radioimmunoassay described by Price et al.’ Each serum sample was assayed in duplicate. Reagents for the radioimmunoassay of 25-OHD, 1,25-(OH),D, and PTH were obtained from the Immunonuclear Corporation, Minneapolis, MN. Reagents for the radioimmunoassay of osteocalcin were
From the Departments of Obstetrics and Gynaecologv, and Orthopaedics, University of Ile-Ife, Nigeria; and the Department of Chemical Pathology and Human Metabolism, The Royal Free Hospital and School of Medicine, London, UK Address reprint requests to P. Dandona, DPhil, FRCP, Director Metabolic Unit, Department of Chemical Pathology and Human Metabolism, The Royal Free Hospital and School of Medicine, London NW3 2QG, UK Copyright 0 1991 by W. B. Saunders Company 0026-0495/91/4002-0018$03.00/0 209
210
OKONOFUA ET AL
Kingdom. The ratio of 1,25-(OH),D to 25OHD was significantly greater in rachitic patients than in controls (Table 2, Fig 2). There was a significant correlation between the 1,25-(OH),D:25-OHD ratio and PTH concentrations in children with rickets (r = .67; P < .05). Serum osteocalcin concentrations in rachitic children were similar to those in controls, but three rachitic children had markedly elevated osteocalcin concentrations. These three children also had the highest 1,25-(OH),D and PTH concentrations (Fig 3). The boy of 9 years with genu valgus also had normal 25-OHD and 1,25-(OH),D concentrations with a low normal calcium, low normal phosphate, and elevated ALP (calcium, 2.10; phosphate, 1.20 mmol/L; ALP, 990 U/L; 25-OHD, 30 nmol/L; PTH-MM, 90 pmol/L). The biochemical data from this patient are not included with the data from other patients. Histology of bone from a sample obtained during a corrective osteotomy in this patient revealed florid rickets with wide osteoid seams (Fig 4). Following the administration of calcium gluconate, plasma ALP activity decreased in all 10 patients (Fig 5), while plasma calcium concentration increased from a median of 2.22 mmol/L to 2.34 mmol/L. X-rays showed radiological healing (Fig 6) and there was resolution of rickets at the clinical level. DISCUSSION
Fig 1. Child with rickets, swollen wrists, and gross genu valga, and rachitic rosary.
obtained from CIS (UK), Bucks, UK. The details of sensitivity and precision of these assays have previously been described.8,9 Statistical analysis was performed by the Mann Whitney U-test for unpaired data.
Our data show that rickets, a condition that is reasonably frequent in Nigeria, especially in poorer sections of population in forested areas, is not associated with either a low 25-OHD or a low 1,25-(OH),D concentration. However, the rachitic children do have lower calcium concentrations, elevated ALP activity, and an increase in serum PTH concentrations. It is also noteworthy that rachitic children do not have significantly lower phosphate concentrations, a feature characteristic of vitamin D deficiency rickets. That plasma phosphate concentrations remain relatively normal is probably attributable to the fact that the phosphate content of this diet is adequate and that increased plasma concentrations of 1,25-(OH),D enhance the efficiency of phosphate absorption. This probably compensates for any urinary loss of phosphate due to secondary hyperparathyroidism. The above facts, in association with our observation that treatment with calcium gluconate causes clinical, radiologi-
RESULTS
Plasma total calcium and albumin-corrected calcium concentrations were significantly lower, and plasma ALP activity consistently higher, in rachitic children than in controls. Plasma phosphate concentrations were not significantly different in the two groups (Table 1). Serum 25OHD concentrations in both groups were similar to each other and were also similar to those found in adult whites in the United Kingdom. Serum 1,25-(OH),D concentrations in patients and controls were not significantly different, but were markedly greater than those observed in white adults and adolescents in the United
Table 1. Plasma Concentrations
of Calcium, Corrected Calcium,
Phosphate, and ALP in Control
Controls (I-I = 12) Rickets (n = 11)
and Rachitic
Ca
Con Ca
(mmollL)
(mmol/L)
Chifdren
PO4
ALP
v-/L)
(U/L)
2.40
2.38
1.70
193
(2.23-2.25)
(2.24-2.50)
(1.30-1.93)
(133-289)
2.22s
2.22*
(1.90-2.43)
(1.62-2.41)
1.36 (0.66-l ,961
(180-740)
412t
NOTE. Values are medians (and range). Abbreviations: Corr Ca, corrected calcium; PO,, phosphate. Statistical analysis: lP < .02; tP < .Ol.
211
RICKETS IN NIGERIAN CHILDREN
Table 2. Serum 25=OHD, 1,25=(OH),D, 1,25(OH),DB=OHD
Ratio, and PTH-Intact, and Osteocalcin Concentrations
in Control and Rachitic Children 250HD n (nmollL) Controls (n = 12) Rickets (n = 10)
Reference ranges (London)
1,25-(OH),D (pmoVL1
1.25125 Ratio
41
178
3.9
(29-50)
(77-294)
(1.6-6.2)
PTH-MM IpmoVLI 54 (33-l 20)
PTH-I WmL)
Osteocalcin WW
14
10.5
(4-55)
(1.0-26.0)
36
203
6.8t
861
60*
16.0
(22-84)
(122-297)
(4.4-10.1)
(47-146)
(6-222)
(4.4-60.0)
15-60
30-120
1.5-3.0
25-85
10-55
2.5-7.0
NOTE. Values are medians (and range). Abbreviations: PTH-MM, PTH mid-molecule; PTH-I, PTH-intact. Statistical analysis: lP i .05; tP < .02.
cal, and biochemical healing of rickets, show that rickets in these children are probably due to primary calcium deficiency rather than vitamin D deficiency. The features of calcium deficiency rickets have previously been shown by Pettifor et al’O~l’to be mild hypocalcemia, normal 25=OHD concentration, secondary hyperparathyroidism, and elevated concentrations of 1,25=(OH),D. Pettifor et al identified these patients from the rural black African population in South Africa and demonstrated that their daily calcium intake was less than 150 mg. They were shown to have clinical, radiological, and histological features typical of rickets, and responded to calcium supplementation alone.” Previous reports of low calcium intake related to rickets range from case reports of pure calcium deficiency’3~‘4to a series of patients with combined calcium and vitamin D deficiency. A calcium intake of less than 150 mg/d along with a high phytate intake would also explain why purdahclad pregnant Nigerian women from poorer economic backgrounds also had lower plasma calcium concentrations while having 25=OHD concentrations greafer than those observed in white women in the United Kingdom.* Our observations have important implications in terms of the pathogenesis, therapy, and preventive aspects of rickets in Nigeria and probably other forested parts of Africa. Our data are particularly relevant to the problem of rickets in forested areas of Nigeria: Ile-Ife is in the rain forest zone 300
where cattle do not survive and dairy products do not form a part of the diet. Any attempt to treat such children should include calcium supplements rather than vitamin D, and the same is probably true for the prevention of this condition. Our findings may also have implications in the pathogenesis of rickets in other tropical parts of the world where sunshine is abundant but rickets and osteomalacia are common. Indeed, Taylor and Marshal-Day in 194015commented on the possible contribution made by dietary calcium deficiency to the pathogenesis of rickets in children in Kangra district in India. The children, many of them almost naked, played in blazing sunshine. The authors could not believe that these children had a significant deficiency of vitamin D. The fact that the ratio of 1,25=(OH),D to 25=OHD is elevated in rachitic children and that it is significantly related to PTH concentrations in this group implies that secondary hyperparathyroidism probably stimulates the conversion of 25=OHD to 1,25=(OH),D in these patients. The cause of secondary hyperparathyroidism in these patients is hypocalcemia following low calcium intake rather than vitamin D deficiency. The absence of a significant elevation of osteocalcin in spite of elevated 1,25= (OH),D and PTH concentrations in rachitic children points to an end organ resistance to the action of 1,25=(OH),D. However, it should be pointed out that three patients with
. : .
250
1
;
z
.
.
.
l**
-
N
A .
:.
FlM.
.
.
..
.
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a 0
0
J 100.
.
Fig 2. Serum 25=OHD, 1,25=(OH),D, concentrations, and the ratio of 1,25=(OH),D to 25=OHD in patients with rickets (R) and controls (Con). The 1,25=(OH),D ratio was significantly greater in patients with rickets (IT) than in controls (Con), while 25=OHD and 1,25=(OH),D concentrations were similar in the two groups.
Fig 3. Serum PTH-MM (mid-molecule), PTH intact (intact molecule), and osteocalcin concentrations in patients with rickets (R) and controls (Con). PTH-MM and PTH-intact concentrations were signfficantfy greater in rachitfc patients than in controls. Serum osteocalcin concentrations were not significantly dffferent.
212
OKONOFUA
Fig 4. Histology of the bone. Note the extensively osteoid seams typical of rickets.
= .
ET AL
thickened
aooc
3 .-
W
Z i
200’
9 i
DAYS OF TREATMENT Fig 5. Serial plasma ALP activity in 10 patients with florid rickets before and after treatment with calcium gluconate.
Fig 6. Radiologiul healing of rickets following cakium gluconate treatment. Knee x-rays (A) befom and (6) after treatment in p8tient 1.
213
RICKETS IN NIGERIAN CHILDREN
markedly elevated osteocalcin concentrations also had high 1,25-(OH),D and PTH levels. 1,25-(OH),D and FTH are known to stimulate osteocalcin production in vitro,‘6r’7while primary hyperparathyroidism is known to be associated with elevated osteocalcin 1evels.7x’s In conclusion, rickets, though frequent in Nigerian children, is due not to vitamin D deficiency, but probably to calcium deficiency. It is associated with hypocalcemia and
secondary hyperparathyroidism. Attempts at treatment or prevention should include calcium supplementation. Further prospective therapeutic studies are required. ACKNOWLEDGMENT
The authors are grateful to Professor E.H.O. Parry for his constructive criticisms of this report and to Pamela Dale for secretarial assistance.
REFERENCES
1. Olatunbosun DA, Adenigi FA, Adadevoh BK: Serum calcium, phosphorous and magnesium levels in pregnant and nonpregnant Nigerians. Br J Obstet Gynaecol82568571,1975 2. Okonofua F, Houlder S, Bell JL, et al: Vitamin D nutrition in pregnant Nigerian women at term and their newborn infants. J Clin Pathol39:650-653,1986 3. Serenius F, Elidressey AHT, Dandona P: Vitamin D malnutrition in pregnant women at term and in newborn infants in Saudi Arabia. J Clin Path01 37:444-447,1984 4. Hummer L, Nilas L, Tjelleson L, et al: A selective and simplified radioimmunoassay of 25hydroxyvitamin D,. Stand J Clin Lab Invest 44:163,1984 5. Reinhardt TA, Horst RL, Orf JW, et al: A microassay for 1,25 dihydroxyvitamin D not requiring high performance liquid chromatography: Application to clinical studies. J Clin Endocrinol Metab 58:91-98,1984 6. Roos B, Linda11AW, Aron DC: Detection and characteristics of small mid region parathyroid hormone fragments in normal and hyperparathyroid gland and sera by immunoextraction and region specific radioimmunoassay. J Clin Endocrinol Metab 53:709-721, 1980 7. Price PA, Parthmore JC, Deftos LJ: New biochemical marker for bone metabolism: measurement by radioimmunoassay of bone GLA protein in plasma of normal subjects and patients with bone disease. J Clin Invest 66:878-885,198O 8. Dandona P, Menon RK, Shenoy S, et al: Low calcitorial concentration, secondary hyperparathyroidism and normal osteocalcin in elderly subjects. J Clin Endocrinol Metab 63:459-462, 1986 9. Menon RK, Gill DS, Thomas M, et al: Impaired carboxyla-
tion of osteoclacin in warfarin treated subjects. J Clin Endocrinol Metab 64:59-60,1987 10. Pettifor JM, Ross FP, Travers R, et al: Dietary calcium deficiency: a syndrome associated with bone deformities and elevated serum 1,25 dihydroxyvitamin D concentration. Metab Bone Dis Rel Res 2:301-305, 1981 11. Pettifor JM, Ross FP, Wang J, et al: Rickets in children of rural origin in South Africa: Is low dietary calcium a factor? J Pediatr 92:320-324,1978 12. Marie PJ, Pettifor JM, Ross FP, et al: Histological osteomalacia due to dietary calcium deficiency in children. N Engl J Med 307:584-588,1982 13. Maltz HE, Fish MB, Holliday MA: Calcium deficiency rickets and the renal response to calcium infusion. Pediatrics 46:865-870,197O 14. Kooh SW, Fraser D, Reidly BJ, et al: Rickets due to calcium deficiency. N Engl J Med 297:1264-1266,1977 15. Taylor GF, Marshal-Day CD: Osteomalacia and dental cares. Br Med J 2:221-222, 1940 16. Skojdt H, Gallagher JA, Beresford JN, et al: Vitamin D metabolites regulate osteocalcin synthesis and proliferation of human bone cells in vitro. J Endocrinol 105:391-396,1985 17. Beresford JN, Gallagher HA, Poser JW, et al: Production of osteocalcin by human bone cells in vitro. Effects of 1,25(OH),D,, 24,25(OH),D,, parathyroid hormone and glucocorticoids. Metab Bone Dis Rel Res 5:229,1984 18. Slovik DM, Gundberg CM, Neer RM, et al: Clinical evaluation of bone turnover by serum osteocalcin measurement in a hospital setting. J Clin Endocrinol Metab 59:228-233, 1984
in Nigerian F. Okonofua,
Children: D.S. Gill, 2.0.
A Consequence Alabi,
M. Thomas,
of Calcium
Malnutrition
J.L. Bell, and P. Dandona
Eleven Nigerian children with clinically and radiologically proven rickets were assessed biochemically. The children had low or low normal concentrations of total and corrected calcium, and elevated plasma alkaline phosphatase (ALP) activity, but normal plasma phosphate concentrations. Their serum 25-hydroxyvitamin D (25.OHD) and 1,25-dihydroxyvitamin D (1,25-(OH&D) concentrations were not significantly different from those in controls, but the ratio of 1,25-(OH&D to 25-OHD was significantly greater than that in controls. Parathyroid hormone (PTH) concentrations were greater in rachitic children, and there was a significant correlation between 1,25-(OH),D and PTH concentrations. Osteocalcin concentrations in rachitic children were not significantly different from those in controls, but they were markedly elevated in the three patients with the highest 1,25-(OH),D and PTH concentrations. One child, from whom a sample of bone (from a corrective osteotomy) was available for histological examination, showed markedly thickened osteoid seams, characteristic of rickets. All the rachitic children had a calcium intake of less than 150 mg daily. Treatment of these rachitic children with calcium gluconate (1 g/d) led to clinical, radiological, and biochemical healing of rickets. We conclude that rickets in Nigerian children is not due to vitamin D deficiency, but to a lack of calcium. This observation has implications regarding the pathogenesis, treatment, and prevention of rickets/osteomalacia in Nigeria and possibly other African and tropical countries. Copyright 0 1991 by W.B. Seunders Compeny
R
ICKETS ARE KNOWN to occur in Nigerian children from the lower socioeconomic groups.’ No biochemical data are available hitherto to establish the pathogenesis of this condition in this population. In a previous study, we have demonstrated that the concentrations of 25hydroxyvitamin D (25OHD) in sera of pregnant Nigerian women are greater than those in pregnant white women in the United Kingdom.’ This was true of even purdah-clad Muslim women in Nigeria, who have lower 25OHD concentrations than those who are not in purdah’; yet the children of purdah-clad Muslim women have a tendency to develop rickets, while those of white women in the United Kingdom do not. In contrast, purdahclad women in Saudi Arabia, whose children also have a tendency to develop rickets, have extremely low 25-OHD concentrations, comparable to those observed in Asian women in the United Kingdom.3 In order to explain this paradox, we have now investigated Nigerian children with rickets and age-matched controls. The observations suggest that the development of rickets in Nigerian children is not primarily due to vitamin D deficiency, but rather is associated with diminished calcium intake. PATIENTS,
MATERIAL,
AND METHODS
Ten Nigerian children (seven boys, three girls) with clinically and radiologically proven rickets, and 12 age-matched controls (nine boys, three girls) were included in the study. The controls had no clinical evidence of rickets or other forms of malnutrition. All children were attending outpatient clinics in University College Hospital in Be-Ife, Nigeria, and were not on any form of treatment. The age of the patients ranged between 3 to 5 years. One additional rachitic patient was included in the study: a boy of 9 years who had clinical and radiological rickets and genu valgus deformity (Fig l), since the operation of corrective osteotomy in this patient provided us with a sample of bone for histological analysis. All patients had painful swellings of wrists and/or knees; x-rays of the region confirmed an irregular expansion of the epiphyseal cartilage. The dietary calcium intake of each of these children was 150 mg/d. The phytate intake of these children was high, since their diet consists mainly of cassava with maize, yam, and plantain. The supply of the latter three is seasonal. There was no milk or any other dairy product in their diet. The dietary intake of calcium was calculated from the total amount of cassava, maize, Metabolism, Vol40, No 2 (February), 1991: pp 209-213
yam, and plaintain consumed, and by multiplying this with the calcium content of each of these foods. The control children had a daily intake of calcium greater than 300 mg. Rachitic children were treated with calcium gluconate 1 g/d for between 40 and 230 days, after which they were lost to follow-up. During the follow-up period, their plasma calcium concentration and alkaline phosphatase (ALP) activity was measured. X-rays were taken to demonstrate radiological healing. Serum samples obtained at follow-up were not large enough for vitamin D and parathyroid hormone (PTH) studies. Blood samples were obtained from the children with rickets and the controls after an overnight fast. Five milliliters blood was collected in heparin; plasma was separated. The remainder was collected in plain glass tubes and allowed to clot. Serum was separated and divided into three aliquots. Plasma and serum samples were frozen immediately at -20°C and stored in this state until they were transported in dry ice to The Royal Free Hospital, London. Plasma calcium, phosphate, ALP, total protein, urea, and electrolyte concentrations were measured on a SMAC Technicon Autoanalyzer. 25-OHD was assayed by the method described by Hummer et al,’ while 1,25-hydroxyvitamin D (1,25-(OH),D) was assayed by the method of Reinhardt et al using a 1,25-(OH),D receptor from calf thymus.5 Serum PTH was measured by a radioimmunoassay using an antibody directed against the mid-fragment of the PTH molecule.6 Osteocalcin concentration was measured by a specific radioimmunoassay described by Price et al.’ Each serum sample was assayed in duplicate. Reagents for the radioimmunoassay of 25-OHD, 1,25-(OH),D, and PTH were obtained from the Immunonuclear Corporation, Minneapolis, MN. Reagents for the radioimmunoassay of osteocalcin were
From the Departments of Obstetrics and Gynaecologv, and Orthopaedics, University of Ile-Ife, Nigeria; and the Department of Chemical Pathology and Human Metabolism, The Royal Free Hospital and School of Medicine, London, UK Address reprint requests to P. Dandona, DPhil, FRCP, Director Metabolic Unit, Department of Chemical Pathology and Human Metabolism, The Royal Free Hospital and School of Medicine, London NW3 2QG, UK Copyright 0 1991 by W. B. Saunders Company 0026-0495/91/4002-0018$03.00/0 209
210
OKONOFUA ET AL
Kingdom. The ratio of 1,25-(OH),D to 25OHD was significantly greater in rachitic patients than in controls (Table 2, Fig 2). There was a significant correlation between the 1,25-(OH),D:25-OHD ratio and PTH concentrations in children with rickets (r = .67; P < .05). Serum osteocalcin concentrations in rachitic children were similar to those in controls, but three rachitic children had markedly elevated osteocalcin concentrations. These three children also had the highest 1,25-(OH),D and PTH concentrations (Fig 3). The boy of 9 years with genu valgus also had normal 25-OHD and 1,25-(OH),D concentrations with a low normal calcium, low normal phosphate, and elevated ALP (calcium, 2.10; phosphate, 1.20 mmol/L; ALP, 990 U/L; 25-OHD, 30 nmol/L; PTH-MM, 90 pmol/L). The biochemical data from this patient are not included with the data from other patients. Histology of bone from a sample obtained during a corrective osteotomy in this patient revealed florid rickets with wide osteoid seams (Fig 4). Following the administration of calcium gluconate, plasma ALP activity decreased in all 10 patients (Fig 5), while plasma calcium concentration increased from a median of 2.22 mmol/L to 2.34 mmol/L. X-rays showed radiological healing (Fig 6) and there was resolution of rickets at the clinical level. DISCUSSION
Fig 1. Child with rickets, swollen wrists, and gross genu valga, and rachitic rosary.
obtained from CIS (UK), Bucks, UK. The details of sensitivity and precision of these assays have previously been described.8,9 Statistical analysis was performed by the Mann Whitney U-test for unpaired data.
Our data show that rickets, a condition that is reasonably frequent in Nigeria, especially in poorer sections of population in forested areas, is not associated with either a low 25-OHD or a low 1,25-(OH),D concentration. However, the rachitic children do have lower calcium concentrations, elevated ALP activity, and an increase in serum PTH concentrations. It is also noteworthy that rachitic children do not have significantly lower phosphate concentrations, a feature characteristic of vitamin D deficiency rickets. That plasma phosphate concentrations remain relatively normal is probably attributable to the fact that the phosphate content of this diet is adequate and that increased plasma concentrations of 1,25-(OH),D enhance the efficiency of phosphate absorption. This probably compensates for any urinary loss of phosphate due to secondary hyperparathyroidism. The above facts, in association with our observation that treatment with calcium gluconate causes clinical, radiologi-
RESULTS
Plasma total calcium and albumin-corrected calcium concentrations were significantly lower, and plasma ALP activity consistently higher, in rachitic children than in controls. Plasma phosphate concentrations were not significantly different in the two groups (Table 1). Serum 25OHD concentrations in both groups were similar to each other and were also similar to those found in adult whites in the United Kingdom. Serum 1,25-(OH),D concentrations in patients and controls were not significantly different, but were markedly greater than those observed in white adults and adolescents in the United
Table 1. Plasma Concentrations
of Calcium, Corrected Calcium,
Phosphate, and ALP in Control
Controls (I-I = 12) Rickets (n = 11)
and Rachitic
Ca
Con Ca
(mmollL)
(mmol/L)
Chifdren
PO4
ALP
v-/L)
(U/L)
2.40
2.38
1.70
193
(2.23-2.25)
(2.24-2.50)
(1.30-1.93)
(133-289)
2.22s
2.22*
(1.90-2.43)
(1.62-2.41)
1.36 (0.66-l ,961
(180-740)
412t
NOTE. Values are medians (and range). Abbreviations: Corr Ca, corrected calcium; PO,, phosphate. Statistical analysis: lP < .02; tP < .Ol.
211
RICKETS IN NIGERIAN CHILDREN
Table 2. Serum 25=OHD, 1,25=(OH),D, 1,25(OH),DB=OHD
Ratio, and PTH-Intact, and Osteocalcin Concentrations
in Control and Rachitic Children 250HD n (nmollL) Controls (n = 12) Rickets (n = 10)
Reference ranges (London)
1,25-(OH),D (pmoVL1
1.25125 Ratio
41
178
3.9
(29-50)
(77-294)
(1.6-6.2)
PTH-MM IpmoVLI 54 (33-l 20)
PTH-I WmL)
Osteocalcin WW
14
10.5
(4-55)
(1.0-26.0)
36
203
6.8t
861
60*
16.0
(22-84)
(122-297)
(4.4-10.1)
(47-146)
(6-222)
(4.4-60.0)
15-60
30-120
1.5-3.0
25-85
10-55
2.5-7.0
NOTE. Values are medians (and range). Abbreviations: PTH-MM, PTH mid-molecule; PTH-I, PTH-intact. Statistical analysis: lP i .05; tP < .02.
cal, and biochemical healing of rickets, show that rickets in these children are probably due to primary calcium deficiency rather than vitamin D deficiency. The features of calcium deficiency rickets have previously been shown by Pettifor et al’O~l’to be mild hypocalcemia, normal 25=OHD concentration, secondary hyperparathyroidism, and elevated concentrations of 1,25=(OH),D. Pettifor et al identified these patients from the rural black African population in South Africa and demonstrated that their daily calcium intake was less than 150 mg. They were shown to have clinical, radiological, and histological features typical of rickets, and responded to calcium supplementation alone.” Previous reports of low calcium intake related to rickets range from case reports of pure calcium deficiency’3~‘4to a series of patients with combined calcium and vitamin D deficiency. A calcium intake of less than 150 mg/d along with a high phytate intake would also explain why purdahclad pregnant Nigerian women from poorer economic backgrounds also had lower plasma calcium concentrations while having 25=OHD concentrations greafer than those observed in white women in the United Kingdom.* Our observations have important implications in terms of the pathogenesis, therapy, and preventive aspects of rickets in Nigeria and probably other forested parts of Africa. Our data are particularly relevant to the problem of rickets in forested areas of Nigeria: Ile-Ife is in the rain forest zone 300
where cattle do not survive and dairy products do not form a part of the diet. Any attempt to treat such children should include calcium supplements rather than vitamin D, and the same is probably true for the prevention of this condition. Our findings may also have implications in the pathogenesis of rickets in other tropical parts of the world where sunshine is abundant but rickets and osteomalacia are common. Indeed, Taylor and Marshal-Day in 194015commented on the possible contribution made by dietary calcium deficiency to the pathogenesis of rickets in children in Kangra district in India. The children, many of them almost naked, played in blazing sunshine. The authors could not believe that these children had a significant deficiency of vitamin D. The fact that the ratio of 1,25=(OH),D to 25=OHD is elevated in rachitic children and that it is significantly related to PTH concentrations in this group implies that secondary hyperparathyroidism probably stimulates the conversion of 25=OHD to 1,25=(OH),D in these patients. The cause of secondary hyperparathyroidism in these patients is hypocalcemia following low calcium intake rather than vitamin D deficiency. The absence of a significant elevation of osteocalcin in spite of elevated 1,25= (OH),D and PTH concentrations in rachitic children points to an end organ resistance to the action of 1,25=(OH),D. However, it should be pointed out that three patients with
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Fig 2. Serum 25=OHD, 1,25=(OH),D, concentrations, and the ratio of 1,25=(OH),D to 25=OHD in patients with rickets (R) and controls (Con). The 1,25=(OH),D ratio was significantly greater in patients with rickets (IT) than in controls (Con), while 25=OHD and 1,25=(OH),D concentrations were similar in the two groups.
Fig 3. Serum PTH-MM (mid-molecule), PTH intact (intact molecule), and osteocalcin concentrations in patients with rickets (R) and controls (Con). PTH-MM and PTH-intact concentrations were signfficantfy greater in rachitfc patients than in controls. Serum osteocalcin concentrations were not significantly dffferent.
212
OKONOFUA
Fig 4. Histology of the bone. Note the extensively osteoid seams typical of rickets.
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DAYS OF TREATMENT Fig 5. Serial plasma ALP activity in 10 patients with florid rickets before and after treatment with calcium gluconate.
Fig 6. Radiologiul healing of rickets following cakium gluconate treatment. Knee x-rays (A) befom and (6) after treatment in p8tient 1.
213
RICKETS IN NIGERIAN CHILDREN
markedly elevated osteocalcin concentrations also had high 1,25-(OH),D and PTH levels. 1,25-(OH),D and FTH are known to stimulate osteocalcin production in vitro,‘6r’7while primary hyperparathyroidism is known to be associated with elevated osteocalcin 1evels.7x’s In conclusion, rickets, though frequent in Nigerian children, is due not to vitamin D deficiency, but probably to calcium deficiency. It is associated with hypocalcemia and
secondary hyperparathyroidism. Attempts at treatment or prevention should include calcium supplementation. Further prospective therapeutic studies are required. ACKNOWLEDGMENT
The authors are grateful to Professor E.H.O. Parry for his constructive criticisms of this report and to Pamela Dale for secretarial assistance.
REFERENCES
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tion of osteoclacin in warfarin treated subjects. J Clin Endocrinol Metab 64:59-60,1987 10. Pettifor JM, Ross FP, Travers R, et al: Dietary calcium deficiency: a syndrome associated with bone deformities and elevated serum 1,25 dihydroxyvitamin D concentration. Metab Bone Dis Rel Res 2:301-305, 1981 11. Pettifor JM, Ross FP, Wang J, et al: Rickets in children of rural origin in South Africa: Is low dietary calcium a factor? J Pediatr 92:320-324,1978 12. Marie PJ, Pettifor JM, Ross FP, et al: Histological osteomalacia due to dietary calcium deficiency in children. N Engl J Med 307:584-588,1982 13. Maltz HE, Fish MB, Holliday MA: Calcium deficiency rickets and the renal response to calcium infusion. Pediatrics 46:865-870,197O 14. Kooh SW, Fraser D, Reidly BJ, et al: Rickets due to calcium deficiency. N Engl J Med 297:1264-1266,1977 15. Taylor GF, Marshal-Day CD: Osteomalacia and dental cares. Br Med J 2:221-222, 1940 16. Skojdt H, Gallagher JA, Beresford JN, et al: Vitamin D metabolites regulate osteocalcin synthesis and proliferation of human bone cells in vitro. J Endocrinol 105:391-396,1985 17. Beresford JN, Gallagher HA, Poser JW, et al: Production of osteocalcin by human bone cells in vitro. Effects of 1,25(OH),D,, 24,25(OH),D,, parathyroid hormone and glucocorticoids. Metab Bone Dis Rel Res 5:229,1984 18. Slovik DM, Gundberg CM, Neer RM, et al: Clinical evaluation of bone turnover by serum osteocalcin measurement in a hospital setting. J Clin Endocrinol Metab 59:228-233, 1984
