J Clin Endocrinol Metab 40: 168, 1975
DISAPPEARANCE OF PLASMA GROWTH HORMONE IN ACROMEGALY AND PROTEIN-CALORIE MALNUTRITION AFTER SOMATOSTATIN B.L. Pimstone, M.D., F.R.C.P. (Lond.), D. Becker, M.B., F.C.P. (S.A.), S. Kronheim, B . S c , Departments of Medicine and Child Health, University of Cape Town, South Africa. ABSTRACT. Plasma human growth hormone (hGH) drops rapidly after somatostatin in adults with acromegaly and infants with protein-calorie malnutrition (PCM) and is linear when plotted logarithmically against time. The half disappearance time (T§) ranged from 28-31* minutes in acromegaly, and 22-23 minutes in PCM. There is no prolongation of plasma hGH clearance in these two diseases. The recently synthesized somatostatin (1) (somatotropin releasing inhibiting factor) acutely inhibits human growth hormone (hGH) secretion in acromegaly (2,3) "by direct action on the anterior pituiThe drop of hGH tary (h) . levels is immediate, affording an opportunity to study its plasma half disappearance time (T|1) and by inference, degradation and excretion. Studies of h'GH T§ in man have usually been performed after intravenous administration of large quantities of unlabelled (5,6) or tracer quantities of radioactively labelled (5,7) growth hormone, and have ranged between 20 and 30 minutes in normal adults. However as the hGH drop is multi-exponential under these experimental conditions (8), the earlier conclusions have been challenged. In PCM plasma hGH levels are grossly elevated and poorly suppressible (9). It has been uncertain as to whether this is the result of hGH hypersecretion or impaired clearance (10). We report here the effects of somatostatin on plasma hGH concentrations in PCM and acromegaly, and suggest that altered plasma clearance is not contributing
to the raised hGH levels. PATIENTS AND METHODS Three adults with pituitary tumours causing clinical acromegaly (verified by elevated, glucose non-suppressible plasma hGH), and four infants aged between 6 months to 3 years suffering from PCM characterised by edema, hypoalbuminemia, dermatosis and low weight for age (10), were studied on the morning after admission to the hospital before commencement of therapy. Informed written consent was obtained from each adult and the mother of each child. Blood was taken into heparinized tubes by venipuncture through an indwelling cannula at 15 minute intervals on two or three occasions before the intravenous administration of somatostatin and at 3,6,9,12, 15,20,30,1*5 and 60 minutes thereafter in the acromegalic subjects, and 3,6,10,15,20, 30 and 1+5 minutes in the malnourished children. The blood was immediately spun and plasma frozen until assayed for hGH by a modification of the double antibody method (11) using NIH-hGH HSI63I1A (Wilhelmi) as
Submitted 9th September, 1971*-• 168 The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 13 November 2015. at 18:32 For personal use only. No other uses without permission. . All rights reserved.
RAPID COMMUNICATIONS
standard, and hGH- 125 I and anti serum provided by CEA-IRE Sorin. Somatostatin (AY2U910, Ayerst) was given in the form of an intravenous bolus of 100 yg followed by 25 yg at 3,6,10,15 and 20 minutes (PCM) and a bolus of 200 yg followed by an infusion of a further 200 yg over 20 minutes (acromegaly). Linear regression analysis of the drop in log hGH concentration against time was carried out by the method of least mean squares, and the T§ by direct extrapolation against the linear component of the curve which was usually 20 and in some instances 30 minutes in duration.
169
100 90 80 70 60 50
W. N. - Kwashiorkor
40
-I
RESULTS In acromegalic subjects, plasma hGH shows a rapid linear decline immediately after intravenous somatostatin when percentage drop is plotted logarithmically against time. The calculated T§ is 31* , 33 and 28 minutes in the 3 patients (Table 1). A similar rapid linear disappearance of endogenous hGH after somatostatin is noted in PCM (Fig. 1). The T§ is 23, 22, 23 and 23 minutes in the k cases (Table 1). DISCUSSION The acute inhibition of hGH release in acromegaly by intravenous somatostatin has enabled us to calculate the disappearance of endogenous hGH. Until now, predictable inhibition of hGH secretion was impossible in acromegalic patients as induced hyperglycemia, which inhibits hGH release in normal subjects (12), does so poorly and unpredictably in that disease (12). Our findings of a
9 TIME
1
1
1
I
l _
12 15 18 21 30 (Minutes)
Fig. 1: An example of the linear decline of plasma hGH over 20 minutes in response to somatostatin in a child with PCM. Tg of 29-31 minutes are similar to data reported in a similar study in acromegaly (3) (in which however, blood was sampled less frequently) as well as to results in normal subjects after exogenous hGH (5,6,7). However the data derived'from exogenous hormone administration is less easy to interpret because the disappearance of the hormone from the vascular pool follows a multi-exponential curve (8), presumably due to initial equilibration of the hormone in various undefined body compartments and because of the varying disappearance times of radioactive hormone fragments. Attempts to calculate endogenous hGH disappearance in acromegaly after hypophysectomy
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 13 November 2015. at 18:32 For personal use only. No other uses without permission. . All rights reserved.
170 Table
RAPID COMMUNICATIONS 1:
I n d i v i d u a l p l a s m a HGH v a l u e s i n p a t i e n t s b e f o r e , d u r i n g and a f t e r S o m a t o s t a t i n ( s e e t e x t ) . HGH ( n g / m l )
-30
Aero. Aero.
305
322
330
68 35 -
67 36 35 k5
69 36 37 kg 68 ko
PCM PCM PCM
-15
70 kk
0
3
6
9
317 307 290 69 65 61 32
33 30
28
66
kk 50 -
38
36
30 L/N
Diagnosi s
Aero. PCM
JCE & M • 1975 Vol 40 t No 1
-
at time
(mins.)
10
15
12
20
-
30
H5
295 2U0 225 220 302 60 60 50 35 33 28 25 22 25 k3 2k 20 31 31 26 3k 29 21 23 35 kk 38 31 >80 k5 33 38 Uo 31 25
(mins)
3k 33 28 23 22 23 23
have also produced discrepant results, our data "being consistent with the findings of Glick et al (13) but at variance with a later report in which growth hormone was found to persist for much longer (6). Possibly in the latter study hGH secretion continued during the course of the test causing overestimation of the T§. Metabolic clearance of hGH in acromegaly measured by constant infusion techniques has been reported as normal However (1^) or low (15). the similarity of our findings to those using radioactive hormone in .normal people, implies that the metabolic clearance rate of hGH in acromegaly is unlikely to be substantially different from normal .
statin was slightly faster than that found in our acromegalics. It is impossible to assess the relevance of this observation as there are no available data on endogenous hGH T§ in normal infants or adults. In the neonate, exogenous unlabelled hGH disappears with a il much shorter than adults (16), but no data on normal infants in the age range of this study are available. The use of pulse doses of somatostatin rather than constant infusion was preferred in the infants for technical reasons. However the intervals between pulses were short, during which time hGH secretion has been shown to remain suppressed (17). This report of endogenous hGH T§ in the range found in normal adult subjects using exogenous hGH, argues against impaired growth hormone clearance in malnutrition.
The pathogenesis of the high plasma hGH so characteristic of PCM remains obscure. It has not been established whether these high levels are a result of hypersecretion or impaired clearance. The drop in plasma hGH in malnourished children after somato-
ACKNOWLEDGMENTS Financial support was obtained from the South African Medical Research Council, Atomic Energy Board and Wellcome Trust. Somatostatin (AY2H910) was generously supplied by Dr. A. Polakow
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 13 November 2015. at 18:32 For personal use only. No other uses without permission. . All rights reserved.
RAPID COMMUNICATIONS of Ayerst Laboratories Ltd., Johannesburg.
(Pty.)
REFERENCES 1. Brazeau, P., W. Vale, R. Burgus , N. Ling, J. Butcher, J. Rivier and R. Guillemin. Science 179: 7 7 , (1973). 2. Hall, R. , G.M. Besser, A.V. Schally, D O H. Coy, D. Evered, D.J. Goldie, A.J. Kastin, A.S. McNeilly, C.H. Mortimer, C. Phenekos, W.M.G. Tunbridge and D. Weightmani Lancet 2:581 , (1973). 3» Yen, S.S.C., T.M. Siler and G.W. De Vane, N.Engl.J. Med. 290:935, (197*0. k, Borgeat, P., F. Labrie, J. Drouin, A. Belanger, H. Immer, K. Sestanj, V o Nelson, M. Gotz, A.V. Schally, D.H. Coy and E.J. Coy. Biochem.biophys.Res. C o m . 56:1052, (197*0. 5. Parker, M.L., R.D. Utiger, W.Ho Daughaday. J.clin.Invest. U1:262, (1962). 6. Refetoff, S«, P.H. Sonksen. Joclin.Endocrinol« 30:386, (1970). 7. Conti , C , M. Negri, A. Isidor, 0. Recchia, L. Sereno. Folia Endocr. 15:721, (1962).
171
8. Cameron, D.P., H.G. Burger, K.J. Catt and A. Doig. J.clin. Invest. 48:1600, (1969). 9. Pimstone, B.L., G. Barbezat, J.D.L. Hansen and P. Murray. Lancet 2:1333, (1967). 10. Pimstone, B.L., D.J. Becker and J.D.L. Hansen. In: Growth and Growth Hormone (1972) Eds. Pecile, A., Miiller, E.E. p.389. Exerpta Medica ICS 244. 11. Morgan, C.R. and Lazarow, A. Diabetes 12:115, (1963). 12. Glick, S.M., J. Roth, R.S. Yalow and S.A. Berson. Rec Progr.Horm.Res. 21:21+1, (1965). 13. Glick, S.M., J. Roth and E.T. Lonergan. J.clin o Endocrinol. 2U:501 , (1964). 14. Taylor, A.L., J.L. Finster and D.H. Mintz. J.clin o Invest. 48:2349, (1969). 15 Thompson, R.G., A, Rodriguez, A. Kowaski and R.M. Blizzard. J.clin.Invest. 51: 3193, (1972). 16. Cornblath, M., M.L. Parker, S.H. Reisner, A.E. Forbes and W.H. Daughaday. J.clin.Endocrinol. 25:209, (1965)17. Prange Hansen, Aa., H. 0rskov, K. Seyer-Hansen and K. Lundbaek. Brit.med.J. 2:523, (1973).
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 13 November 2015. at 18:32 For personal use only. No other uses without permission. . All rights reserved.
DISAPPEARANCE OF PLASMA GROWTH HORMONE IN ACROMEGALY AND PROTEIN-CALORIE MALNUTRITION AFTER SOMATOSTATIN B.L. Pimstone, M.D., F.R.C.P. (Lond.), D. Becker, M.B., F.C.P. (S.A.), S. Kronheim, B . S c , Departments of Medicine and Child Health, University of Cape Town, South Africa. ABSTRACT. Plasma human growth hormone (hGH) drops rapidly after somatostatin in adults with acromegaly and infants with protein-calorie malnutrition (PCM) and is linear when plotted logarithmically against time. The half disappearance time (T§) ranged from 28-31* minutes in acromegaly, and 22-23 minutes in PCM. There is no prolongation of plasma hGH clearance in these two diseases. The recently synthesized somatostatin (1) (somatotropin releasing inhibiting factor) acutely inhibits human growth hormone (hGH) secretion in acromegaly (2,3) "by direct action on the anterior pituiThe drop of hGH tary (h) . levels is immediate, affording an opportunity to study its plasma half disappearance time (T|1) and by inference, degradation and excretion. Studies of h'GH T§ in man have usually been performed after intravenous administration of large quantities of unlabelled (5,6) or tracer quantities of radioactively labelled (5,7) growth hormone, and have ranged between 20 and 30 minutes in normal adults. However as the hGH drop is multi-exponential under these experimental conditions (8), the earlier conclusions have been challenged. In PCM plasma hGH levels are grossly elevated and poorly suppressible (9). It has been uncertain as to whether this is the result of hGH hypersecretion or impaired clearance (10). We report here the effects of somatostatin on plasma hGH concentrations in PCM and acromegaly, and suggest that altered plasma clearance is not contributing
to the raised hGH levels. PATIENTS AND METHODS Three adults with pituitary tumours causing clinical acromegaly (verified by elevated, glucose non-suppressible plasma hGH), and four infants aged between 6 months to 3 years suffering from PCM characterised by edema, hypoalbuminemia, dermatosis and low weight for age (10), were studied on the morning after admission to the hospital before commencement of therapy. Informed written consent was obtained from each adult and the mother of each child. Blood was taken into heparinized tubes by venipuncture through an indwelling cannula at 15 minute intervals on two or three occasions before the intravenous administration of somatostatin and at 3,6,9,12, 15,20,30,1*5 and 60 minutes thereafter in the acromegalic subjects, and 3,6,10,15,20, 30 and 1+5 minutes in the malnourished children. The blood was immediately spun and plasma frozen until assayed for hGH by a modification of the double antibody method (11) using NIH-hGH HSI63I1A (Wilhelmi) as
Submitted 9th September, 1971*-• 168 The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 13 November 2015. at 18:32 For personal use only. No other uses without permission. . All rights reserved.
RAPID COMMUNICATIONS
standard, and hGH- 125 I and anti serum provided by CEA-IRE Sorin. Somatostatin (AY2U910, Ayerst) was given in the form of an intravenous bolus of 100 yg followed by 25 yg at 3,6,10,15 and 20 minutes (PCM) and a bolus of 200 yg followed by an infusion of a further 200 yg over 20 minutes (acromegaly). Linear regression analysis of the drop in log hGH concentration against time was carried out by the method of least mean squares, and the T§ by direct extrapolation against the linear component of the curve which was usually 20 and in some instances 30 minutes in duration.
169
100 90 80 70 60 50
W. N. - Kwashiorkor
40
-I
RESULTS In acromegalic subjects, plasma hGH shows a rapid linear decline immediately after intravenous somatostatin when percentage drop is plotted logarithmically against time. The calculated T§ is 31* , 33 and 28 minutes in the 3 patients (Table 1). A similar rapid linear disappearance of endogenous hGH after somatostatin is noted in PCM (Fig. 1). The T§ is 23, 22, 23 and 23 minutes in the k cases (Table 1). DISCUSSION The acute inhibition of hGH release in acromegaly by intravenous somatostatin has enabled us to calculate the disappearance of endogenous hGH. Until now, predictable inhibition of hGH secretion was impossible in acromegalic patients as induced hyperglycemia, which inhibits hGH release in normal subjects (12), does so poorly and unpredictably in that disease (12). Our findings of a
9 TIME
1
1
1
I
l _
12 15 18 21 30 (Minutes)
Fig. 1: An example of the linear decline of plasma hGH over 20 minutes in response to somatostatin in a child with PCM. Tg of 29-31 minutes are similar to data reported in a similar study in acromegaly (3) (in which however, blood was sampled less frequently) as well as to results in normal subjects after exogenous hGH (5,6,7). However the data derived'from exogenous hormone administration is less easy to interpret because the disappearance of the hormone from the vascular pool follows a multi-exponential curve (8), presumably due to initial equilibration of the hormone in various undefined body compartments and because of the varying disappearance times of radioactive hormone fragments. Attempts to calculate endogenous hGH disappearance in acromegaly after hypophysectomy
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 13 November 2015. at 18:32 For personal use only. No other uses without permission. . All rights reserved.
170 Table
RAPID COMMUNICATIONS 1:
I n d i v i d u a l p l a s m a HGH v a l u e s i n p a t i e n t s b e f o r e , d u r i n g and a f t e r S o m a t o s t a t i n ( s e e t e x t ) . HGH ( n g / m l )
-30
Aero. Aero.
305
322
330
68 35 -
67 36 35 k5
69 36 37 kg 68 ko
PCM PCM PCM
-15
70 kk
0
3
6
9
317 307 290 69 65 61 32
33 30
28
66
kk 50 -
38
36
30 L/N
Diagnosi s
Aero. PCM
JCE & M • 1975 Vol 40 t No 1
-
at time
(mins.)
10
15
12
20
-
30
H5
295 2U0 225 220 302 60 60 50 35 33 28 25 22 25 k3 2k 20 31 31 26 3k 29 21 23 35 kk 38 31 >80 k5 33 38 Uo 31 25
(mins)
3k 33 28 23 22 23 23
have also produced discrepant results, our data "being consistent with the findings of Glick et al (13) but at variance with a later report in which growth hormone was found to persist for much longer (6). Possibly in the latter study hGH secretion continued during the course of the test causing overestimation of the T§. Metabolic clearance of hGH in acromegaly measured by constant infusion techniques has been reported as normal However (1^) or low (15). the similarity of our findings to those using radioactive hormone in .normal people, implies that the metabolic clearance rate of hGH in acromegaly is unlikely to be substantially different from normal .
statin was slightly faster than that found in our acromegalics. It is impossible to assess the relevance of this observation as there are no available data on endogenous hGH T§ in normal infants or adults. In the neonate, exogenous unlabelled hGH disappears with a il much shorter than adults (16), but no data on normal infants in the age range of this study are available. The use of pulse doses of somatostatin rather than constant infusion was preferred in the infants for technical reasons. However the intervals between pulses were short, during which time hGH secretion has been shown to remain suppressed (17). This report of endogenous hGH T§ in the range found in normal adult subjects using exogenous hGH, argues against impaired growth hormone clearance in malnutrition.
The pathogenesis of the high plasma hGH so characteristic of PCM remains obscure. It has not been established whether these high levels are a result of hypersecretion or impaired clearance. The drop in plasma hGH in malnourished children after somato-
ACKNOWLEDGMENTS Financial support was obtained from the South African Medical Research Council, Atomic Energy Board and Wellcome Trust. Somatostatin (AY2H910) was generously supplied by Dr. A. Polakow
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 13 November 2015. at 18:32 For personal use only. No other uses without permission. . All rights reserved.
RAPID COMMUNICATIONS of Ayerst Laboratories Ltd., Johannesburg.
(Pty.)
REFERENCES 1. Brazeau, P., W. Vale, R. Burgus , N. Ling, J. Butcher, J. Rivier and R. Guillemin. Science 179: 7 7 , (1973). 2. Hall, R. , G.M. Besser, A.V. Schally, D O H. Coy, D. Evered, D.J. Goldie, A.J. Kastin, A.S. McNeilly, C.H. Mortimer, C. Phenekos, W.M.G. Tunbridge and D. Weightmani Lancet 2:581 , (1973). 3» Yen, S.S.C., T.M. Siler and G.W. De Vane, N.Engl.J. Med. 290:935, (197*0. k, Borgeat, P., F. Labrie, J. Drouin, A. Belanger, H. Immer, K. Sestanj, V o Nelson, M. Gotz, A.V. Schally, D.H. Coy and E.J. Coy. Biochem.biophys.Res. C o m . 56:1052, (197*0. 5. Parker, M.L., R.D. Utiger, W.Ho Daughaday. J.clin.Invest. U1:262, (1962). 6. Refetoff, S«, P.H. Sonksen. Joclin.Endocrinol« 30:386, (1970). 7. Conti , C , M. Negri, A. Isidor, 0. Recchia, L. Sereno. Folia Endocr. 15:721, (1962).
171
8. Cameron, D.P., H.G. Burger, K.J. Catt and A. Doig. J.clin. Invest. 48:1600, (1969). 9. Pimstone, B.L., G. Barbezat, J.D.L. Hansen and P. Murray. Lancet 2:1333, (1967). 10. Pimstone, B.L., D.J. Becker and J.D.L. Hansen. In: Growth and Growth Hormone (1972) Eds. Pecile, A., Miiller, E.E. p.389. Exerpta Medica ICS 244. 11. Morgan, C.R. and Lazarow, A. Diabetes 12:115, (1963). 12. Glick, S.M., J. Roth, R.S. Yalow and S.A. Berson. Rec Progr.Horm.Res. 21:21+1, (1965). 13. Glick, S.M., J. Roth and E.T. Lonergan. J.clin o Endocrinol. 2U:501 , (1964). 14. Taylor, A.L., J.L. Finster and D.H. Mintz. J.clin o Invest. 48:2349, (1969). 15 Thompson, R.G., A, Rodriguez, A. Kowaski and R.M. Blizzard. J.clin.Invest. 51: 3193, (1972). 16. Cornblath, M., M.L. Parker, S.H. Reisner, A.E. Forbes and W.H. Daughaday. J.clin.Endocrinol. 25:209, (1965)17. Prange Hansen, Aa., H. 0rskov, K. Seyer-Hansen and K. Lundbaek. Brit.med.J. 2:523, (1973).
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 13 November 2015. at 18:32 For personal use only. No other uses without permission. . All rights reserved.
