Suppression of Luteinizing Hormone in Castrated Women by the Administration of Human Chorionic Gonadotropin AKIRA MIYAKE, OSAMU TANIZAWA, TOSHIHIRO AONO, MOTOI YASUDA, AND KEIICHI KURACHI Department of Obstetrics and Gynecology, Osaka University Medical School, Osaka, 533, Japan ABSTRACT. The suppressive effect of human chorionic gonadotropin (hCG) on luteinizing hormone (LH) and/or LH-/3 was studied by specific LH-/3 radioimmunoassay following hCG administration. Eight castrated women were each administered 10,000 IU of hCG in a single intramuscular injection and five women in the control group were injected with saline. The serum level of hCG increased after the injection, reaching 217.6 mlU/ml after 8 h. There was a significant suppression of the LH levels as compared to those of the control group
S
and the pre-injection levels: 68.2% 1 h after injection, 64.7% after 2 h, 65.5% after 4 h, 77.0% after 8 h, 78.6% after 12 h, and 78.2% after 24 h. There was no significant suppression of the follicle-stimulating hormone (FSH) as compared to the preinjection and control values. Serum concentration of estradioli was not detectable either before or after the hCG injection. We conclude that hCG has a suppressive effect on LH and/or LH-/3 secretion not mediated by estradiol. (/ Clin Endocrinol Metab 43: 928, 1976)
EVERAL studies suggest that gonadotropims possess a short feedback mechanism. The implantation of LH in the median eminence area of a rat suppresses the LH content in the pituitary and in the blood (1-5). The administration of follicle-stimulating hormone (FSH) reduces the gonadotropin releasing factor activity in the rat hypothalamus (6-9). The following three experimental procedures decrease pituitary LH and FSH contents and ovarian weight in the rat, and strongly suggest the presence of a short feedback mechanism: 1) administration of pregnant mare serum gonadotropin (PMSG) (10,11); 2) implantation of PMSG to the medial basal hypothalamus (12); and 3) implantation of human chorionic gonadotropin (hCG) (13). In agonadal human subjects, Reiter and associates (14) reported that there was no change in serum FSH following the administration of hCG. However, it was still unresolved whether or not exogenous hCG had any effect on serum LH levels, because LH and hCG were not distinguished by conventional immunoassay. For this study, LH was measured without interference from hCG with a LH-/3-anti-LH-/3 radioimmunoassay (RIA) and the addition of a sufficient quantity of hCG to the reaction tubes to eliminate on cross-reaction. Using this RIA system, the direct effect of hCG on LH secretion in castrated women was investigated.
Received March 9, 1976.
Materials and Methods Thirteen women, ranging in age from 33 to 60 who had undergone total hysterectomy and bilateral oophorectomy more than 2 weeks prior to the study because of uterine cancer, volunteered for our study. Eight of these women received 10,000 IU of hCG (Mochida Pharmaceutical Co., Tokyo) in a single im injection at 0800 h, while the remaining five were given im injections of saline. Blood samples were taken prior to the injections and after 1, 2, 4, 8, 12, and 24 h. The separated serum was stored at - 1 5 C until assayed. All samples from one individual were measured in the same assay run. To measure LH or LH-/3 subunit concentration in each serum, a modification of the double-antibody RIA system, using LH-/3 and anti-LH-/3 of Calbiochem (La Jolla, Calif.), was utilized. The LH-/3 was iodinated by a modification of the Greenwood-Hunter's method to specific activities of 50-136 /xCi//ig. Employing this method, 50 IU of hCG (16.7 ixg) was added to each reaction tube in order to diminish potential cross-reactivity of antiserum to hCG. Forty per cent binding of tracer was obtained with a final dilution of 1:10,000 of anti LH-/3 sera. Using this RIA method, the minimum detectable dose of LH-/3 was 0.04 ng/ml, the intraassay and interassay coefficients of variation were 7.5% and 15.1%, and the mean recovery was 102.2 ± 8.6% (Mean ± SE). The mean recovery measured by the addition of LH-/3 in dose levels of 0.075, 0.15, 0.3, 0.6, 1.2, and 2.4 ng to 0.2 ml of serum 2 h after the administration of hCG was 99.4 ± 3.0% (Mean ± SE). The rate of cross-reactivity with LH (WHO 68/40) was 14.1%, 2.5% with FSH (Calbiochem), and 4.0% with TSH (NIH 68/38). No cross-reaction was observed
928
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 01 October 2015. at 10:46 For personal use only. No other uses without permission. . All rights reserved.
COMMENTS with the addition of either hCG (CR 115) 4 /xg/ml, hCG-a subunit (CR 115) 200 ng/ml, or hCG-/3 subunit (Mochida) 400 ng/ml. Concentrations of hPRL (NIAMD), hGH (Wilhelmi), and ACTH (Richter) within normal ranges did not have any effect on this RIA system (Fig. 1). Serum FSH levels were measured by the RIA method previously described (15). The Second International Reference Preparation of Human Menopausal Gonadotropin (IRP-HMG) was used as a standard for FSH and expressed as mlU 2nd IRP-HMG/ml serum. Comparison of the relative potency of the 2nd IRPHMG and pituitary standard LER 907 in our assay system revealed 40 mIU//u,g for FSH. The concentration of hCG in the serum was measured by hCG-RIA utilizing hCG (CR 115)-anti-hCG-/3 (16) supplied by NIAMD. The Second International Standard for hCG was used, and the value was expressed as mlU/ml. Serum levels of estradiol (E2) were measured by RIA, using essentially the same method as Wu and Lundy (17). The minimum detectable dose in our laboratory was 10.0 pg/ml, and coefficients of variation were 4.0% (intraassay) and 15.1% (interassay) respectively. Statistical analysis of the data was performed by unpaired Student's t test.
Results Serum levels of LH, FSH, and hCG before and after the hCG injection are summarized in Table 1 and Fig. 2. LH concentrations as expressed in weight of WHO 68/40 were calculated with conversion factor of 7.1 = 100/14.1 from immunoreactive LH-/3 values. Serum hCG reached a peak of 217.6 mlU/ml 8 h after the hCG injection and the level gradually decreased to 182.0 mlU/ml 24 h after the injection. In contrast, LH showed a significant decrease after the hCG in-
929
jection compared with the pre-injection level; i.e. 68.2% after 1 h, 64.7% after 2 h, 65.5% after 4 h, 77.0% after 8 h, 78.6% after 12 h and 78.2% after 24 h. Suppression of serum LH concentrations expressed as per cent of baseline in the hCG-injected group was significant (P < 0.010.05) compared with serum LH levels in the control group which received saline. On the other hand, the serum FSH level was within 93.1106.3% of the pre-injection value in both the hCGinjected and control groups, and no significant difference was observed. Serum concentration of E2 was not detectable either before or after the hCG injection. Discussion The present LH-/3 RIA system was not affected in the measurement of LH-/3 even by the presence of 500 IU/ml of hCG. The maximum serum level of hCG after the im injection of 10,000 IU of hCG was 217.6 mlU/ml, and this level did not interfere with our RIA system. The recovery of 99.4% of LH-/3 added to the serum obtained 2 h after the injection of hCG indicates the absence of a factor or factors that might affect the value of LH-j8 measurement. This LH-/3 assay had a 14.1% cross reactivity by weight with native LH. Therefore our RIA system detected not only isolated LH-/3 but also native LH. As the low or undetectable concentration of LH-/3 level was demonstrated by gel filtration in postmenopausal women (18,19), it seems likely that the immunoreactive LH-/3 levels consist mainly of native LH rather than of LH-/3. Therefore, immunoreactive LH-/3 values were multiplied by conversion factor of 7.1 = 100/14.1 to obtain LH concentra-
99f-
FIG. 1. Cross-reaction of the intact protein hormones and their subunits in the specific LH-/3 radioimmunoassay. Results are expressed in terms of the logit of B/Bo x 100 vs. the log of the dose.
10' ng/mfi
103
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 01 October 2015. at 10:46 For personal use only. No other uses without permission. . All rights reserved.
2.27
1.92 0.67
1.56 0.35
2.41
0.78
1.61
0.38
1.74
2.77
2.77
1.10
2.14
0.32
1.07
2.32
0.44
1.63
3.27
2.52
1.14
2.49
2.21
0.37
50
49
44
38
61
53
50
44
33
7
8
1
Mean
: SE
6
Mean
± SE
5
2
3
4
5
2.31
0.43
2.27
2.98
1.10
3.27
2.56
1.42
0.39
2.15
2.34
1.03
2.88
3.02
1.49
0.35
1.53
0.38
0.85
0.43
1.78
0.43
1.99
50
4
0.65
1.70 2.36
1.78 3.12
1.78
3.49
1.87
4.12
51
3
0.61
1.14
0.14
1.11
1.31
54
3.91 1.14
3.10
2.41
2.27
3.12
60
LH (ng/ml)
4
Time (h)
1
2
1
0
0.51
1.91
2.34
0.64
3.02
—
1.63
0.30
1.72
1.17
0.78
2.63
1.14
3.05
1.65
0.97
2.40
8
24
0.43
2.30
3.12
1.21
1.81
3.51
1.85
0.92
2.05
2.06
1.31
2.34
3.30
1.24
Control group
0.27
0.43
75.0
11.1
53.1
78.0
34.5
31.0
11.8
60.4
90.0
42.0
21.7
101.0
47.5
13.9
13.3
47.0
72.8
80.5
—
0.67 74.3
86.3
55.0
0.71
0.57
1.89
59.0
65.0
1.89
66.0 62.5
62.5
1.56 2.49
2.20
2.84
2.06
46.0
39.0 154.0
45.5 155.0
2.13
1.79 4.26
14.5
60.1
78.0
38.5
25.0
97.0
62.0
7.5
68.9
78.0
63.0
71.5
70.0
102.0
39.5
75.0 40.5
35.5
81.0
2
95.0
1
1.29
1.93
0
0.99
2.56
HCG treated group
12
8.3
51.5
58.5
45.0
27.0
71.0
56.0
9.9
8.6
43.8
65.5
35.5
33.0
—
41.0
11.7
72.2
10.8
46.1
64.5
33.0
33.0
78.0
40.5
13.6
77.6
70.5 72.3
63.5 70.0
11.9
53.3
71.0
37.0
23.5
80.0
55.0
9.9
63.8
—
60.0
70.0 70.0 55.5
41.0 66.5
49.0 100.5
45.0
41.5
81.0
24
135.0
78.0
69.5
53.0
130.0
39.0
131.0
12
65.0
65.0
80.0
125.0
48.5
43.0
43.0
108.0
42.0
8
80.0
FSH (mlU/ml)
4
Time (h)
Serum concentrations of LH and FSH in castrated women following injections of hCG or saline; LH concentrations as expressed from immunoreactive LH-/3 values in weight of WHO 68/40 were calculated with conversion factor of 7.1 =
2
N o . Age
TABLE 1.
o £m -a• • z >=
C/5
H
w
on
930
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 01 October 2015. at 10:46 For personal use only. No other uses without permission. . All rights reserved.
COMMENTS tions. The intraassay coefficient variation of 7.5% shows that 25% lowering of the LH level in the serum 1-24 h after the hCG injection is a significant suppression. Compared with the LH levels of the control group, the decrease in women who received hCG was statistically significant at all times during 1-12 h after the hCG injection; therefore this decrease cannot be considered as a diurnal variation. Serum E2 levels did not exceed the detectable level even after the hCG injection. Poliak and associates (20,21) reported that urinary excretion of estrogen and 17-ketosteroids did not increase in castrated women after an injection of 50,000 IU of hCG. These facts strongly suggest that the lowering of LH after the administration of hCG is due to the direct feedback effect of hCG on the hypothalamo-pituitary system rather than for E2It has been reported that exogenous gonadotropin suppresses LH-RF and LH secretion in rats (22). Hirono and associates (13) reported that the implantation of hCG into the median eminence of a rat caused a decrease in both pituitary content and serum concentration of LH. Our present results confirmed this phenomenon in women. It is not possible to distinguish from the present results whether the site of exogenous hCG action is the hypothalamus or the anterior pituitary. However, the hypothalamus is more likely the primary site of action of hCG, because Hirono and associates (13) reported that the implantation of hCG into the pituitary had little influence on production and secretion of LH in rats. This may be clarified by the measurement of hypothalamic LH-RH after the administration of hCG. Acknowledgments The authors are grateful to Drs. K. Matsumoto and K. Miyai for reviewing the manuscript. We wish to express appreciation to Daiichi Radioidotope Laboratories for LH-/3 Kit, to the National Institute of Arthritis, Metabolism, and Digestive Disease, USA for HCG-/3 RIA Kit, and to the National Institute for Medical Research, England for 2nd IRP-HMG and 2nd International Standard hCG.
References 1. Corbin, A., and A. I. Cohen, Effect of median eminence implants of LH on pituitary LH of female rats, Endocrinology 78: 41, 1966. 2. David, M. A., F. Fraschini, and L. Martini, Control of LH secretion: Role of a "short" feedback mechanism, Endocrinology 78: 55, 1966.
931 120
100
80
60
200
E
100
24
FIG. 2. Mean ± SE changes in serum LH and FSH concentrations expressed as per cent of preinjection levels and mean ± SE concentrations of serum hCG after the hCG or saline injection in castrated women. Statistical analysis was performed by unpaired Student's t test between hCG and saline injected groups. hCG vs. control: * P < 0.05, ** P < 0.01. 3. Corbin, A., Pituitary and plasma LH of ovariectomized rats with median eminence implants of LH, Endocrinology 78: 893, 1966. 4. Hirono, M., M. Igarashi, and S. Matsumoto, Short- and auto-feedback mechanism of LH, Endocrinoljap 18: 175, 1971. 5. Docke, F., and D. Glaser, Internal feedback of luteinizing hormone in cyclic female rats, J Endocrinol 51: 403, 1971. 6. Corbin, A., and J. C. Story, "Internal" feedback mechanism: Response of pituitary FSH and of stalk-
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 01 October 2015. at 10:46 For personal use only. No other uses without permission. . All rights reserved.
932
7. 8. 9.
10. 11.
12.
13.
14.
COMMENTS median eminence follicle stimulating hormonereleasing factor to median eminence implants of FSH, Endocrinology 80: 1006, 1967. Franschini, F., M. Motta, and L. Martini, A 'short' feedback mechanism controlling FSH secretion, Experientia 24: 270, 1968. Hirono, M., M. Igarashi, and S. Matsumoto, Short- and auto-feedback control of pituitary FSH secretion, Neuroendocrinology 6: 274, 1970. Corbin, A., E. L. Daniels, and J. E. Milmore, An "internal" feedback mechanism controlling follicle stimulating hormone releasing factor, Endocrinology 86: 735, 1970. Szontagh, F. E., S. Uhlarik, and A. Jakobovits, The effect of gonadotropic hormones on the hypophysis of the rat, Ada Endocrinol (Kbh) 41: 31, 1962. Szontagh, F. E., and S. Uhlarik, The possiblity of a direct 'internal' feedback in the control of pituitary gonadotrophin secretion, / Endocrinol 29: 203, 1964. Arai, Y., and R. A. Gorski, Inhibition of ovarian compensatory hypertrophy by hypothalamic implantation of gonadotrophin in androgen-sterilized rats: Evidence for "internal" feedback, Endocrinology 82: 871, 1968. Hirono, M., M. Igarashi, and S. Matsumoto, The direct effect of hCG upon pituitary gonadotrophin secretion, Endocrinology 90: 1214, 1972. Reiter, E. 0., H. E. Kulin, and D. L. Loriaux, FSH suppression during short term hCG administra-
15.
16.
17. 18. 19. 20.
21.
22.
JCE & M • 1976 Vol 43 • No 4
tion: A gonadally mediated process,/ Clin Endocrinol Metab 34: 1080, 1972. Aono, T., and M. L. Taymor, Radioimmunoassay for follicle-stimulating hormone (FSH) with I25Ilabeled FSH, Am J Obstet Gynecol 100: 110, 1968. Vaitukaitis, J. L., G. D. Braunstein, and G. T. Ross, A radioimmunoassay which specifically measures human chorionic gonadotropin in the presence of human luteinizing hormone, Am J Obstet Gynecol 113: 751, 1972. Wu, C-H., and L. E. Lundy, Radioimmunoassay of plasma estrogens, Steroids 18: 91, 1971. Prentice, L. G., and R. J. Ryan, LH and its subunits in human pituitary, serum and urine,/ Clin Endocrinol Metab 40: 303, 1975. Hagen, C , Identification of human FSH, LH and its subunits in foetal and adult pituitary glands, Acta Endocrinol [Suppl](Kbh) 199: 91, 1975. Poliak, A., G. E. S. Jones, and J. D. Woodruff, The effect of human chorionic gonadotropin on castrated postmenopausal women, Am J Obstet Gynecol 109: 555, 1971. Poliak, A., J. J. Smith, D. Friedlander, and S. L. Romney, Estrogen synthesis in castrated women: The action of human chorionic gonadotropin and corticotropin, Am J Obstet Gynecol 110: 376, 1971. Nallar, R., and A. M. Biscardi, Hypophyseal feedback in the hypothalamic regulation of luteinizing hormone secretion, Experientia 29: 878, 1973.
Third Latin American Congress on Diabetes The Third Latin American Congress on Diabetes, organized by the Latin American Diabetes Association, will be held in Lima, Peru on May 15-19, 1977. An adequate number of lectures, symposia, round table discussions, and short communications have been scheduled. For further information, write to: Dr. Rolando Calderon, P.O. Box 843, Lima, Perii.
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 01 October 2015. at 10:46 For personal use only. No other uses without permission. . All rights reserved.
S
and the pre-injection levels: 68.2% 1 h after injection, 64.7% after 2 h, 65.5% after 4 h, 77.0% after 8 h, 78.6% after 12 h, and 78.2% after 24 h. There was no significant suppression of the follicle-stimulating hormone (FSH) as compared to the preinjection and control values. Serum concentration of estradioli was not detectable either before or after the hCG injection. We conclude that hCG has a suppressive effect on LH and/or LH-/3 secretion not mediated by estradiol. (/ Clin Endocrinol Metab 43: 928, 1976)
EVERAL studies suggest that gonadotropims possess a short feedback mechanism. The implantation of LH in the median eminence area of a rat suppresses the LH content in the pituitary and in the blood (1-5). The administration of follicle-stimulating hormone (FSH) reduces the gonadotropin releasing factor activity in the rat hypothalamus (6-9). The following three experimental procedures decrease pituitary LH and FSH contents and ovarian weight in the rat, and strongly suggest the presence of a short feedback mechanism: 1) administration of pregnant mare serum gonadotropin (PMSG) (10,11); 2) implantation of PMSG to the medial basal hypothalamus (12); and 3) implantation of human chorionic gonadotropin (hCG) (13). In agonadal human subjects, Reiter and associates (14) reported that there was no change in serum FSH following the administration of hCG. However, it was still unresolved whether or not exogenous hCG had any effect on serum LH levels, because LH and hCG were not distinguished by conventional immunoassay. For this study, LH was measured without interference from hCG with a LH-/3-anti-LH-/3 radioimmunoassay (RIA) and the addition of a sufficient quantity of hCG to the reaction tubes to eliminate on cross-reaction. Using this RIA system, the direct effect of hCG on LH secretion in castrated women was investigated.
Received March 9, 1976.
Materials and Methods Thirteen women, ranging in age from 33 to 60 who had undergone total hysterectomy and bilateral oophorectomy more than 2 weeks prior to the study because of uterine cancer, volunteered for our study. Eight of these women received 10,000 IU of hCG (Mochida Pharmaceutical Co., Tokyo) in a single im injection at 0800 h, while the remaining five were given im injections of saline. Blood samples were taken prior to the injections and after 1, 2, 4, 8, 12, and 24 h. The separated serum was stored at - 1 5 C until assayed. All samples from one individual were measured in the same assay run. To measure LH or LH-/3 subunit concentration in each serum, a modification of the double-antibody RIA system, using LH-/3 and anti-LH-/3 of Calbiochem (La Jolla, Calif.), was utilized. The LH-/3 was iodinated by a modification of the Greenwood-Hunter's method to specific activities of 50-136 /xCi//ig. Employing this method, 50 IU of hCG (16.7 ixg) was added to each reaction tube in order to diminish potential cross-reactivity of antiserum to hCG. Forty per cent binding of tracer was obtained with a final dilution of 1:10,000 of anti LH-/3 sera. Using this RIA method, the minimum detectable dose of LH-/3 was 0.04 ng/ml, the intraassay and interassay coefficients of variation were 7.5% and 15.1%, and the mean recovery was 102.2 ± 8.6% (Mean ± SE). The mean recovery measured by the addition of LH-/3 in dose levels of 0.075, 0.15, 0.3, 0.6, 1.2, and 2.4 ng to 0.2 ml of serum 2 h after the administration of hCG was 99.4 ± 3.0% (Mean ± SE). The rate of cross-reactivity with LH (WHO 68/40) was 14.1%, 2.5% with FSH (Calbiochem), and 4.0% with TSH (NIH 68/38). No cross-reaction was observed
928
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 01 October 2015. at 10:46 For personal use only. No other uses without permission. . All rights reserved.
COMMENTS with the addition of either hCG (CR 115) 4 /xg/ml, hCG-a subunit (CR 115) 200 ng/ml, or hCG-/3 subunit (Mochida) 400 ng/ml. Concentrations of hPRL (NIAMD), hGH (Wilhelmi), and ACTH (Richter) within normal ranges did not have any effect on this RIA system (Fig. 1). Serum FSH levels were measured by the RIA method previously described (15). The Second International Reference Preparation of Human Menopausal Gonadotropin (IRP-HMG) was used as a standard for FSH and expressed as mlU 2nd IRP-HMG/ml serum. Comparison of the relative potency of the 2nd IRPHMG and pituitary standard LER 907 in our assay system revealed 40 mIU//u,g for FSH. The concentration of hCG in the serum was measured by hCG-RIA utilizing hCG (CR 115)-anti-hCG-/3 (16) supplied by NIAMD. The Second International Standard for hCG was used, and the value was expressed as mlU/ml. Serum levels of estradiol (E2) were measured by RIA, using essentially the same method as Wu and Lundy (17). The minimum detectable dose in our laboratory was 10.0 pg/ml, and coefficients of variation were 4.0% (intraassay) and 15.1% (interassay) respectively. Statistical analysis of the data was performed by unpaired Student's t test.
Results Serum levels of LH, FSH, and hCG before and after the hCG injection are summarized in Table 1 and Fig. 2. LH concentrations as expressed in weight of WHO 68/40 were calculated with conversion factor of 7.1 = 100/14.1 from immunoreactive LH-/3 values. Serum hCG reached a peak of 217.6 mlU/ml 8 h after the hCG injection and the level gradually decreased to 182.0 mlU/ml 24 h after the injection. In contrast, LH showed a significant decrease after the hCG in-
929
jection compared with the pre-injection level; i.e. 68.2% after 1 h, 64.7% after 2 h, 65.5% after 4 h, 77.0% after 8 h, 78.6% after 12 h and 78.2% after 24 h. Suppression of serum LH concentrations expressed as per cent of baseline in the hCG-injected group was significant (P < 0.010.05) compared with serum LH levels in the control group which received saline. On the other hand, the serum FSH level was within 93.1106.3% of the pre-injection value in both the hCGinjected and control groups, and no significant difference was observed. Serum concentration of E2 was not detectable either before or after the hCG injection. Discussion The present LH-/3 RIA system was not affected in the measurement of LH-/3 even by the presence of 500 IU/ml of hCG. The maximum serum level of hCG after the im injection of 10,000 IU of hCG was 217.6 mlU/ml, and this level did not interfere with our RIA system. The recovery of 99.4% of LH-/3 added to the serum obtained 2 h after the injection of hCG indicates the absence of a factor or factors that might affect the value of LH-j8 measurement. This LH-/3 assay had a 14.1% cross reactivity by weight with native LH. Therefore our RIA system detected not only isolated LH-/3 but also native LH. As the low or undetectable concentration of LH-/3 level was demonstrated by gel filtration in postmenopausal women (18,19), it seems likely that the immunoreactive LH-/3 levels consist mainly of native LH rather than of LH-/3. Therefore, immunoreactive LH-/3 values were multiplied by conversion factor of 7.1 = 100/14.1 to obtain LH concentra-
99f-
FIG. 1. Cross-reaction of the intact protein hormones and their subunits in the specific LH-/3 radioimmunoassay. Results are expressed in terms of the logit of B/Bo x 100 vs. the log of the dose.
10' ng/mfi
103
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 01 October 2015. at 10:46 For personal use only. No other uses without permission. . All rights reserved.
2.27
1.92 0.67
1.56 0.35
2.41
0.78
1.61
0.38
1.74
2.77
2.77
1.10
2.14
0.32
1.07
2.32
0.44
1.63
3.27
2.52
1.14
2.49
2.21
0.37
50
49
44
38
61
53
50
44
33
7
8
1
Mean
: SE
6
Mean
± SE
5
2
3
4
5
2.31
0.43
2.27
2.98
1.10
3.27
2.56
1.42
0.39
2.15
2.34
1.03
2.88
3.02
1.49
0.35
1.53
0.38
0.85
0.43
1.78
0.43
1.99
50
4
0.65
1.70 2.36
1.78 3.12
1.78
3.49
1.87
4.12
51
3
0.61
1.14
0.14
1.11
1.31
54
3.91 1.14
3.10
2.41
2.27
3.12
60
LH (ng/ml)
4
Time (h)
1
2
1
0
0.51
1.91
2.34
0.64
3.02
—
1.63
0.30
1.72
1.17
0.78
2.63
1.14
3.05
1.65
0.97
2.40
8
24
0.43
2.30
3.12
1.21
1.81
3.51
1.85
0.92
2.05
2.06
1.31
2.34
3.30
1.24
Control group
0.27
0.43
75.0
11.1
53.1
78.0
34.5
31.0
11.8
60.4
90.0
42.0
21.7
101.0
47.5
13.9
13.3
47.0
72.8
80.5
—
0.67 74.3
86.3
55.0
0.71
0.57
1.89
59.0
65.0
1.89
66.0 62.5
62.5
1.56 2.49
2.20
2.84
2.06
46.0
39.0 154.0
45.5 155.0
2.13
1.79 4.26
14.5
60.1
78.0
38.5
25.0
97.0
62.0
7.5
68.9
78.0
63.0
71.5
70.0
102.0
39.5
75.0 40.5
35.5
81.0
2
95.0
1
1.29
1.93
0
0.99
2.56
HCG treated group
12
8.3
51.5
58.5
45.0
27.0
71.0
56.0
9.9
8.6
43.8
65.5
35.5
33.0
—
41.0
11.7
72.2
10.8
46.1
64.5
33.0
33.0
78.0
40.5
13.6
77.6
70.5 72.3
63.5 70.0
11.9
53.3
71.0
37.0
23.5
80.0
55.0
9.9
63.8
—
60.0
70.0 70.0 55.5
41.0 66.5
49.0 100.5
45.0
41.5
81.0
24
135.0
78.0
69.5
53.0
130.0
39.0
131.0
12
65.0
65.0
80.0
125.0
48.5
43.0
43.0
108.0
42.0
8
80.0
FSH (mlU/ml)
4
Time (h)
Serum concentrations of LH and FSH in castrated women following injections of hCG or saline; LH concentrations as expressed from immunoreactive LH-/3 values in weight of WHO 68/40 were calculated with conversion factor of 7.1 =
2
N o . Age
TABLE 1.
o £m -a• • z >=
C/5
H
w
on
930
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 01 October 2015. at 10:46 For personal use only. No other uses without permission. . All rights reserved.
COMMENTS tions. The intraassay coefficient variation of 7.5% shows that 25% lowering of the LH level in the serum 1-24 h after the hCG injection is a significant suppression. Compared with the LH levels of the control group, the decrease in women who received hCG was statistically significant at all times during 1-12 h after the hCG injection; therefore this decrease cannot be considered as a diurnal variation. Serum E2 levels did not exceed the detectable level even after the hCG injection. Poliak and associates (20,21) reported that urinary excretion of estrogen and 17-ketosteroids did not increase in castrated women after an injection of 50,000 IU of hCG. These facts strongly suggest that the lowering of LH after the administration of hCG is due to the direct feedback effect of hCG on the hypothalamo-pituitary system rather than for E2It has been reported that exogenous gonadotropin suppresses LH-RF and LH secretion in rats (22). Hirono and associates (13) reported that the implantation of hCG into the median eminence of a rat caused a decrease in both pituitary content and serum concentration of LH. Our present results confirmed this phenomenon in women. It is not possible to distinguish from the present results whether the site of exogenous hCG action is the hypothalamus or the anterior pituitary. However, the hypothalamus is more likely the primary site of action of hCG, because Hirono and associates (13) reported that the implantation of hCG into the pituitary had little influence on production and secretion of LH in rats. This may be clarified by the measurement of hypothalamic LH-RH after the administration of hCG. Acknowledgments The authors are grateful to Drs. K. Matsumoto and K. Miyai for reviewing the manuscript. We wish to express appreciation to Daiichi Radioidotope Laboratories for LH-/3 Kit, to the National Institute of Arthritis, Metabolism, and Digestive Disease, USA for HCG-/3 RIA Kit, and to the National Institute for Medical Research, England for 2nd IRP-HMG and 2nd International Standard hCG.
References 1. Corbin, A., and A. I. Cohen, Effect of median eminence implants of LH on pituitary LH of female rats, Endocrinology 78: 41, 1966. 2. David, M. A., F. Fraschini, and L. Martini, Control of LH secretion: Role of a "short" feedback mechanism, Endocrinology 78: 55, 1966.
931 120
100
80
60
200
E
100
24
FIG. 2. Mean ± SE changes in serum LH and FSH concentrations expressed as per cent of preinjection levels and mean ± SE concentrations of serum hCG after the hCG or saline injection in castrated women. Statistical analysis was performed by unpaired Student's t test between hCG and saline injected groups. hCG vs. control: * P < 0.05, ** P < 0.01. 3. Corbin, A., Pituitary and plasma LH of ovariectomized rats with median eminence implants of LH, Endocrinology 78: 893, 1966. 4. Hirono, M., M. Igarashi, and S. Matsumoto, Short- and auto-feedback mechanism of LH, Endocrinoljap 18: 175, 1971. 5. Docke, F., and D. Glaser, Internal feedback of luteinizing hormone in cyclic female rats, J Endocrinol 51: 403, 1971. 6. Corbin, A., and J. C. Story, "Internal" feedback mechanism: Response of pituitary FSH and of stalk-
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 01 October 2015. at 10:46 For personal use only. No other uses without permission. . All rights reserved.
932
7. 8. 9.
10. 11.
12.
13.
14.
COMMENTS median eminence follicle stimulating hormonereleasing factor to median eminence implants of FSH, Endocrinology 80: 1006, 1967. Franschini, F., M. Motta, and L. Martini, A 'short' feedback mechanism controlling FSH secretion, Experientia 24: 270, 1968. Hirono, M., M. Igarashi, and S. Matsumoto, Short- and auto-feedback control of pituitary FSH secretion, Neuroendocrinology 6: 274, 1970. Corbin, A., E. L. Daniels, and J. E. Milmore, An "internal" feedback mechanism controlling follicle stimulating hormone releasing factor, Endocrinology 86: 735, 1970. Szontagh, F. E., S. Uhlarik, and A. Jakobovits, The effect of gonadotropic hormones on the hypophysis of the rat, Ada Endocrinol (Kbh) 41: 31, 1962. Szontagh, F. E., and S. Uhlarik, The possiblity of a direct 'internal' feedback in the control of pituitary gonadotrophin secretion, / Endocrinol 29: 203, 1964. Arai, Y., and R. A. Gorski, Inhibition of ovarian compensatory hypertrophy by hypothalamic implantation of gonadotrophin in androgen-sterilized rats: Evidence for "internal" feedback, Endocrinology 82: 871, 1968. Hirono, M., M. Igarashi, and S. Matsumoto, The direct effect of hCG upon pituitary gonadotrophin secretion, Endocrinology 90: 1214, 1972. Reiter, E. 0., H. E. Kulin, and D. L. Loriaux, FSH suppression during short term hCG administra-
15.
16.
17. 18. 19. 20.
21.
22.
JCE & M • 1976 Vol 43 • No 4
tion: A gonadally mediated process,/ Clin Endocrinol Metab 34: 1080, 1972. Aono, T., and M. L. Taymor, Radioimmunoassay for follicle-stimulating hormone (FSH) with I25Ilabeled FSH, Am J Obstet Gynecol 100: 110, 1968. Vaitukaitis, J. L., G. D. Braunstein, and G. T. Ross, A radioimmunoassay which specifically measures human chorionic gonadotropin in the presence of human luteinizing hormone, Am J Obstet Gynecol 113: 751, 1972. Wu, C-H., and L. E. Lundy, Radioimmunoassay of plasma estrogens, Steroids 18: 91, 1971. Prentice, L. G., and R. J. Ryan, LH and its subunits in human pituitary, serum and urine,/ Clin Endocrinol Metab 40: 303, 1975. Hagen, C , Identification of human FSH, LH and its subunits in foetal and adult pituitary glands, Acta Endocrinol [Suppl](Kbh) 199: 91, 1975. Poliak, A., G. E. S. Jones, and J. D. Woodruff, The effect of human chorionic gonadotropin on castrated postmenopausal women, Am J Obstet Gynecol 109: 555, 1971. Poliak, A., J. J. Smith, D. Friedlander, and S. L. Romney, Estrogen synthesis in castrated women: The action of human chorionic gonadotropin and corticotropin, Am J Obstet Gynecol 110: 376, 1971. Nallar, R., and A. M. Biscardi, Hypophyseal feedback in the hypothalamic regulation of luteinizing hormone secretion, Experientia 29: 878, 1973.
Third Latin American Congress on Diabetes The Third Latin American Congress on Diabetes, organized by the Latin American Diabetes Association, will be held in Lima, Peru on May 15-19, 1977. An adequate number of lectures, symposia, round table discussions, and short communications have been scheduled. For further information, write to: Dr. Rolando Calderon, P.O. Box 843, Lima, Perii.
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 01 October 2015. at 10:46 For personal use only. No other uses without permission. . All rights reserved.
