Evaluation of hypothalamic–pituitary–adrenal axis in amenorrhoeic women with insulin-dependent diabetes

A. la Marca, G. Morgante and V. De Leo1

Department of Obstetrics and Gynecology, University of Siena, Viale Bracci, 53100 Siena, Italy


    Abstract
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Diabetes is associated with a higher incidence of secondary hypogonadotrophic amenorrhoea. In amenorrhoeic women with insulin-dependent diabetes a derangement in hypothalamic–pituitary–ovary axis has been proposed. No data exist on hypothalamic–pituitary–adrenal function in these women. Gonadotrophin releasing hormone (GnRH), corticotrophin releasing hormone (CRH), metoclopramide and thyroid releasing hormone (TRH) tests were performed in 15 diabetic women, eight amenorrhoeic (AD) and seven eumenorrhoeic (ED). Frequent blood samples were taken during 24 h to evaluate cortisol plasma concentrations. There were no differences between the groups in body mass index, duration of diabetes, insulin dose and metabolic control. The AD women had lower plasma concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin, oestradiol, androstenedione and 17-hydroxyprogesterone (17-OHP) than the ED women. The responses of pituitary gonadotrophins to GnRH, and of thyroid stimulating hormone (TSH) to TRH, were similar in both groups. The AD women had a lower prolactin response to TRH and metoclopramide, and lower ACTH and cortisol responses to CRH, than the ED women. Mean cortisol concentrations >24 h were higher in the amenorrhoeic group. Significant differences in cortisol concentrations from 2400 to 1000 h were found between the two groups. Insulin-dependent diabetes may involve mild chronic hypercortisolism which may affect metabolic control. Stress-induced activation of the hypothalamic–pituitary–adrenal axis would increase hypothalamic secretion of CRH. This would lead directly and perhaps also indirectly by increasing dopaminergic tonus to inhibition of GnRH secretion and hence hypogonadotrophic amenorrhoea. Amenorrhoea associated with metabolically controlled insulin-dependent diabetes is a form of functional hypothalamic amenorrhoea that requires pharmacological and psychological management.

Key words: ACTH/adrenal androgens/amenorrhoea/cortisol/diabetes mellitus


    Introduction
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
It has been shown that 30% of young women with insulin-dependent diabetes mellitus are affected by menstrual irregularity (Bergqvist, 1954Go). The prevalence of secondary amenorrhoea in diabetic women is 8.2% compared to only 2.8% in the normal female population (Kiaer et al., 1992Go); however, the age of onset and mean duration of amenorrhoea do not seem to differ between the two populations. In a previous study it has been reported (Kjar et al., 1992) that amenorrhoea in diabetic women is associated with a low body mass index (BMI) and high concentrations of glycosylated haemoglobin (HbA1c), indicating that underweight and poor metabolic control may be partly responsible for the preponderance of amenorrhoea in this population. Other authors (Djursing et al., 1982Go) have not found any relationship between metabolic state and menstrual irregularity in women with insulin-dependent diabetes. In a longitudinal study, it was demonstrated (O'Hare et al., 1987Go) that improvement in metabolic and nutritional status was not associated with a spontaneous return of menstruation. Some authors have reported altered pituitary secretion of luteinizing hormone (LH) (Distiller et al., 1975Go) and reduced response of LH to luteinizing hormone-releasing hormone (LHRH) (Djursing et al., 1983Go) in diabetic patients with amenorrhoea while others reported a normal (Grossman et al., 1982Go) or enhanced LH response (South et al., 1993Go).

It has been postulated that diabetic amenorrhoeic women have increased dopaminergic tonus that could play a role in the pathogenesis of amenorrhoea (Djursing et al., 1983Go, 1984Go). Berga et al. (1991) found increased dopaminergic tonus and accelerated LH pulsatility after administration of a dopamine antagonist in women with functional hypothalamic amenorrhoea. They also reported a variety of neuroendocrine aberrations in patients with functional hypothalamic amenorrhoea (Berga et al., 1989Go). In these patients, increased activity of the hypothalamic–pituitary–adrenal axis, demonstrated by increased cortisol concentrations, may play a primary role in the pathogenesis of amenorrhoea (Berga et al., 1997Go). The aim of this study was to investigate the hypothalamic–pituitary–ovary and hypothalamic–pituitary–adrenal axis in young amenorrhoeic women with insulin-dependent diabetes in good metabolic control.


    Materials and methods
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Patients
Fifteen women with diabetes mellitus (eight amenorrhoeic and seven eumenorrhoeic) were enrolled in the present study. All patients were treated with insulin, were normotensive, had good kidney function and did not suffer from ketoacidosis. Metabolic control was evaluated by measurement of blood glucose and blood HbA1c concentrations. Mean age, age at menarche, mean BMI, duration of amenorrhoea, duration of diabetes, insulin dose and HbA1c concentrations are given in Table IGo. In amenorrhoeic patients, amenorrhoea developed 3.8 ± 1.4 (mean ± SD) years after the onset of diabetes. No differences in daily exercise energy expenditure or diet were found between the groups.


View this table:
[in this window]
[in a new window]
 
Table I. Clinical data of amenorrhoeic diabetic (AD) and eumenorrhoeic diabetic (ED) women with insulin dependent diabetes
 
Women with other causes of amenorrhoea, such as hyperprolactinaemia, thyroid and adrenal disorders, premature ovarian failure and polycystic ovary syndrome were not included in the study. Women with pathological affective disorders as defined by the Diagnostic and Statistical Manual of Mental Disorders (1994) were also excluded.

Procedures
The women were admitted to the Gynecological Endocrinology Hospital Centre of Siena University 2 h before blood sampling was to begin. Eumenorrhoeic patients were investigated in midfollicular phase. All patients were administered conventional regular and intermediate acting insulin (s.c. injections twice daily). An indwelling catheter was inserted in the antecubital vein and saline solution was infused slowly to keep the vein patent. Blood samples were taken every 30 min from 0800–1000 h, 1200–1400 h, 1600–1800 h, 2000–2200 h, 2400–0200 h and 0400–0600 h. Sleeping was permitted only from 2300 to 0700 h. At 0800 h next day, all patients did the combined releasing hormone test simultaneously [100 µg corticotrophin releasing hormone (CRH; Nova Biochem, Zurich, Switzerland), 100 µg gonadotrophin releasing hormone (GnRH; Biochem Immunosystems, Milan, Italy), 200 µg thyrotrophin releasing hormone (TRH; Biochem Immunosystems)]. Blood samples were taken at –20, –10, 0, 15, 30, 45, 60, 75, 90, 105 and 120 min. A portion of the blood was immediately placed in EDTA-treated plastic tubes. The next day, i.v. metoclopramide (10 mg; Plasil; Lepetit, Frosinone, Italy) was administered. Blood samples were taken at –15, 0, 15, 30, 45 and 60 min.

Hormone assays
Plasma follicle stimulating hormone (FSH), LH, oestradiol, thyroid stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), prolactin, cortisol, dihydroepiandrosterone sulphate (DHEAS), androstenedione, 17-hydroxyprogesterone (17-OHP), sex hormone-binding globulin (SHBG), testosterone, free testosterone, free triiodothyronine and free thyroxine concentrations were assayed by double-antibody radioimmunoassay using commercial kits from Radim (Rome, Italy) for FSH, LH, cortisol, DHEAS, androstenedione and TSH, from Sorin (Saluggia-VC, Italy) for oestradiol and testosterone, from Biodata (Rome, Italy) for prolactin, from DPC (Los Angeles, CA, USA) for ACTH, SHBG, 17-OHP and free testosterone and from Immunotech (Marseille, France) for free thyroxine and free triiodothyronine. Samples were assayed in duplicate at two dilutions. Samples from a given subject were analysed for each hormone in the same assay to avoid inter-assay variation. Quality control pools at low, normal and high LH, FSH, oestradiol, prolactin, TSH, ACTH, testosterone, free testosterone, free triiodothyronine, free thyroxine, androstenedione, 17-OHP, SHBG, DHEAS and cortisol concentrations were present in each assay. The detection limit of the assay was 0.20 IU/l for LH, 0.18 IU/l for FSH, 18 pmol/l for oestradiol, 2.4 nmol/l for cortisol, 277 pmol/l for testosterone, 0.5 pmol/l for free testosterone, 1.7 pmol/l for ACTH, 0.2 mIU/l for TSH, 0.05 µmol/l for DHEAS, 0.21 nmol/l for 17-OHP, 0.2 nmol/l for SHBG, 104 pmol/ for androstenedione, 0.4 pmol/l for free triiodothyronine, 0.4 nmol/l for free thyroxine and 0.3 µg/l for prolactin. Intra- and interassay variations were 7.8 and 8.2% for LH, 6.2 and 6.5% for FSH, 4 and 4.8% for 17-OHP, 4.9 and 7.2% for DHEAS, 5.6 and 6.4% for androstenedione, 4.2 and 4.9% for oestradiol, 4.8 and 6% for cortisol, 3.4 and 4.6% for testosterone, 4.6 and 4.7% for free testosterone, 4.9 and 6.4% for ACTH, 6.1 and 8% for SHBG, 3.1 and 2.5% for TSH, 5.15 and 5.5% for free triiodothyronine, 3.9 and 3.3% for free thyroxine and 3.4 and 1.6% for prolactin.

Statistical analysis
The results are expressed as means and SD. The total integrated hormonal responses to GnRH, TRH, CRH and metoclopramide were calculated by the trapezoidal method and expressed as the area under the concentration–time curve (AUC). Non-Gaussian-distributed variables were logarithmically transformed before analysis. For clarity the non-log-transformed data are presented in the tables and figures. Analysis of variance was performed to detect time-related differences. To compare the differences between the groups peak values (the maximum rise above baseline values) and the areas under curve were compared using Student's t-test. Statistical significance was taken for P < 0.05.


    Results
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Table IIGo shows basal concentrations of gonadotrophins, TSH, prolactin, thyroid hormones, ovarian steroids, adrenal steroids and SHBG of amenorrhoeic diabetic (AD) and eumenorrhoeic diabetic (ED) women. Concentrations of LH, FSH, prolactin, oestradiol, androstenedione and 17-OHP were lower in AD than ED women (P < 0.05). There were no differences in basal concentrations of the other hormones between the two groups.


View this table:
[in this window]
[in a new window]
 
Table II. Basal hormone plasma concentrations in amenorrhoeic diabetic (AD) and eumenorrhoeic diabetic (ED) women
 
GnRH test
Administration of GnRH was followed by similar total and incremental LH and FSH peaks in both groups (38 ± 7.5 versus 41.5 ± 9.2 IU/l and 7.3 ± 2.1 versus 7.6 ± 2.5 IU/l respectively). There were no differences in AUC of LH and FSH between groups (30 ± 9.5 versus 32 ± 12 IU/l.time and 4.8 ± 1.7 versus 5.3 ± 2.1 IU/l.time respectively) (data not shown).

TRH test
There were no differences in total, incremental and AUC responses of TSH to TRH between the two groups. TRH administration was followed by a lower incremental response of prolactin in AD than in ED (140 ± 35 versus 185 ± 43 µg/l; P < 0.05). The AUC of prolactin was significantly smaller in AD than in ED (75 ± 18 versus 103 ± 28 µg/l.time; P < 0.05) (data not shown).

Metoclopramide test
This drug was followed by a larger total and incremental response of prolactin in ED than in AD (P < 0.05). In the latter group, the AUC was significantly smaller than in ED (P < 0.05) (Figure 1Go).



View larger version (15K):
[in this window]
[in a new window]
 
Figure 1. The total increase in prolactin and the cumulated response (area under the curve) of prolactin to metoclopramide were significantly lower in amenorrhoeic diabetic women (AD, open bar) than in eumenorrhoeic diabetic women (ED, closed bar). Values are mean ± SD. *P < 0.05.

 
CRH test
CRH administration was followed by a lower total and incremental response of ACTH in AD than in ED (P < 0.05). The AUC of the ACTH response was significantly less in the AD group (P < 0.05) (Figure 2Go). CRH administration was followed by a larger incremental cortisol response in ED than AD (P < 0.01). The AUC of cortisol was significantly less in the AD group (P < 0.05) (Figure 3Go).



View larger version (13K):
[in this window]
[in a new window]
 
Figure 2. The total increase in adrenocorticotrophic hormone (ACTH) and the cumulated response (area under the curve) of ACTH to corticotrophin releasing hormone (CRH) were significantly lower in amenorrhoeic diabetic women (AD, open bar) than in eumenorrhoeic diabetic women (ED, closed bar). Values are mean ± SD. *P < 0.05.

 


View larger version (15K):
[in this window]
[in a new window]
 
Figure 3. The maximum increase in cortisol and the cumulated response (AUC) of cortisol to CRH were significantly lower in amenorrhoeic diabetic women (AD, open bar) than in eumenorrhoeic diabetic women (ED, closed bar). Values are mean ± SD. *P < 0.05.

 
24 h cortisol pattern
Women in the AD group had higher mean 24 h cortisol concentrations than those in the ED group (350 ± 70 versus 250 ± 40 nmol/l; P < 0.01) (Figure 4Go). Significant differences (P < 0.01) in cortisol plasma concentrations between the two groups were observed from 2400 to 1000 h. The daytime (1200–2200 h) values did not differ between groups (Figure 5Go).



View larger version (13K):
[in this window]
[in a new window]
 
Figure 4. Mean 24 h cortisol plasma concentrations in amenorrhoeic diabetic (AD, open bar) and eumenorrhoeic diabetic (ED, closed bar) women. Values are mean ± SD. *P < 0.01.

 


View larger version (16K):
[in this window]
[in a new window]
 
Figure 5. Cortisol plasma concentrations were significantly higher in amenorrhoic diabetic (AD, open bars) women than in eumenorrhoeic diabetic (ED, closed bars) women from 2400 to 1000 h. Values are mean ± SD. *P < 0.01.

 

    Discussion
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Although the number of patients studied was small, the present results show that the diabetes patients with amenorrhoea had lower basal concentrations of pituitary gonadotrophins and oestradiol than the eumenorrhoeic diabetics. A non-diabetic control group was not included in the protocol because the main purpose of the study was to detect hormonal differences between eumenorrhoeic and amenorrhoeic diabetic women. The AD group had slightly elevated gonadotrophins but this was in part due to the assay methods. In the ED group, basal FSH and the FSH/LH ratio were slightly elevated because the blood samples were performed in midfollicular phase (before 10th day of cycle) when FSH may still have been higher than LH. It has long been known that diabetes is associated with a higher incidence of secondary hypogonadotrophic amenorrhoea than found in the general population (Kiaer et al., 1992Go). The onset of amenorrhoea has been linked to poor metabolic control, but it has since been demonstrated in longitudinal studies that improved metabolic control was not followed by normalization of basal hormone concentrations and a return of menstrual cyclicity (O'Hare et al., 1987Go).

In the present study two groups of women with insulin-dependent diabetes were compared; there were no differences in duration of diabetes, metabolic control and BMI. As in certain other studies, no differences in the response of pituitary gonadotrophins to GnRH were found. However, there is disagreement in the literature, some authors reporting an enhanced and others an inhibited response of LH to GnRH. Administration of TRH was followed by a normal and similar response of TSH in both groups of patients. Basal plasma concentrations of prolactin were significantly lower in the amenorrhoeic group than in the eumenorrhoeic one, and the TRH response expressed as maximum increment and AUC was lower in the amenorrhoeic women and similar to that observed in women with functional hypothalamic amenorrhoea (Berga et al., 1989Go).

Administration of metoclopramide was followed by lower pituitary secretion of prolactin in the amenorrhoeic group than in the eumenorrhoeic one, in line with the results of other studies (Djursing et al., 1983Go). This finding of reduced prolactin response to antidopaminergic central drug is explained by an increase in dopaminergic tonus. In diabetic women, administration of metoclopramide causes an increase in gonadotrophins (Djursing et al., 1985Go). Similar results were also seen (Berga et al., 1991Go) in non-diabetic women with functional hypothalamic amenorrhoea. In one study performed in men with poorly controlled diabetes (Iranmesh et al., 1990Go) a reduction in prolactin pulse amplitude has been reported, suggesting increased dopaminergic tonus. In women an increment of dopaminergic tonus could be partly responsible for amenorrhoea due to inhibition of GnRH secretion.

To our knowledge, there is no data in the literature on the activity of the hypothalamic–pituitary–adrenal axis in amenorrhoeic women with insulin-dependent diabetes. Administration of CRH caused a lower increase in ACTH concentrations in AD women and the AUC was significantly less in amenorrhoeic patients. The maximum increment and AUC of cortisol to CRH were significantly lower in the amenorrhoeic group. The 24 h mean concentrations of cortisol were signficantly higher in the amenorrhoeic group than in the eumenorrhoeic one. Significant differences in plasma concentrations of cortisol between 2400 and 1000 h were also found between the two groups while significant differences were not found during the day.

Taken as a whole, these findings indicate activation of the hypothalamic–pituitary–adrenal axis in diabetic amenorrhoeic patients. In a previous study it has been demonstrated (Wurzburger et al., 1990Go) that diabetics showed significant reductions in cortisol concentrations as metabolic control improved. The present results suggest that for a given metabolic status, amenorrhoeic patients have amplified cortisol concentrations and hyperactivity of the hypothalamic–pituitary–adrenal axis. Similar results have been reported in non-diabetic women with functional hypothalamic amenorrhoea (Berga et al., 1997Go). Other studies have reported a reduction in the response of cortisol to CRH (Biller et al., 1990Go; Nappi et al., 1993Go) in women with functional hypothalamic amenorrhoea with respect to eumenorrhoeic women. It is well known that hyperactivity of the hypothalamic–pituitary–adrenal axis inhibits the hypothalamic–pituitary–ovarian axis, causing amenorrhoea. CRH is one of the main mediators of stress-induced inhibition of gonadotrophin secretion (Rivier et al., 1986Go). In fact, central administration of CRH decreases LH secretion in rats and monkeys (Ono et al., 1984Go; Olster et al., 1987). This reduction seems to be unrelated to increased adrenal steroid secretion, since the reduction in LH after CRH infusion in adrenalectomized monkeys is reported to be similar to that in normal monkeys (Xiao et al., 1989Go). Diabetes mellitus is associated with low concentrations of insulin-like growth factor-I (IGF-I) and high concentrations of IGF binding protein-1 (IGFBP-1), a protein down-regulated by insulin (Hanaire-Broutin et al., 1996Go). Even intensified s.c. insulin therapy does not normalize IGF-I plasma concentrations. It has been demonstrated that insulin, IGF-I and IGF-II play a role in modulating gonadotrophin-mediated folliculogenesis and steroidogenesis. Both insulin and IGF-I receptors are present in the human ovary (Poretsky and Kalin, 1987Go). An autocrine function of IGF-I is suggested by its ability to amplify the FSH induction of LH receptors, progesterone sythesis and aromatase activity (Erickson et al., 1989Go; Adashi et al., 1990Go). Recently, a decrease in ovarian cytochrome P450c17{alpha} activity has been shown after reduction of insulin secretion by metformin in polycystic ovary syndrome (Nestler and Jakubowicz, 1996Go).

It is also difficult to exclude the possibility that diabetes itself affects adrenal function. Evidence of adrenal hyperfunction has been reported in uncomplicated diabetes mellitus (Coiro et al., 1995Go). Dissociation of cortisol and DHEAS secretion has been found in children with insulin-dependent diabetes (Radetti et al., 1994Go) and it has been proposed that insulin has a direct effect on the biosynthetic pathway of adrenal steroids (Ghizzoni et al., 1993Go). It is therefore possible that insulin-dependent diabetes involves mild chronic hypercortisolism, probably by paracrine mechanisms, and this condition may affect metabolic control. Subsequent stress-induced activation of the hypothalamic–pituitary–adrenal axis would enhance hypothalamic secretion of CRH which directly, and perhaps also indirectly through an increase in dopaminergic tonus, may inhibit GnRH secretion, leading to hypogonadotropic amenorrhoea.

In conclusion, the identification of the amenorrhoea associated with insulin-dependent diabetes with good metabolic control as a form of functional hypothalamic amenorrhoea is of considerable interest, because functional hypothalamic amenorrhoea is, by definition, `a theoretically reversible form of ovulatory impairment' requiring psychological and pharmacological management.


    Notes
 
1 To whom correspondence should be addressed Back


    References
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Adashi, E.Y., Resnick, C.E., Hernandez, E.R. et al. (1990) Follicle-stimulating hormone inhibits the constitutive release of insulin-like growth factor binding proteins by cultured rat ovarian granulosa cells. Endocrinology, 126, 1305–1311.[Abstract]

Berga, S.L., Mortola, J.F., Girton, L. et al. (1989) Neuroendocrine aberrations in women with functional hypothalamic amenorrhea. J. Clin. Endocrinol. Metab., 68, 301–307.[Abstract]

Berga, S.L., Loucks, A.B., Rossmanith, W.G. et al. (1991) Acceleration of luteinizing hormone pulse frequency in functional hypothalamic amenorrhea by dopaminergic blockade. J. Clin. Endocrinol. Metab., 72, 151–156.[Abstract]

Berga, S.L., Daniels, T.L. and Giles, D.E. (1997) Women with functional hypothalamic amenorrhea but not other forms of anovulation display amplified cortisol concentrations. Fertil. Steril., 67, 1024–1030.[ISI][Medline]

Bergqvist, N. (1954) The gonadal function in female diabetics. Acta Endocrinol., 19 (Suppl.), 3–20.

Biller, B.M.K., Federoff, H.J., Koenig, J.I. et al. (1990) Abnormal cortisol secretion and responses to corticotropin-releasing hormone in women with hypothalamic amenorrhea. J. Clin. Endocrinol. Metab.,70, 311–3117.[Abstract]

Coiro, V., Volpi, R., Capretti, L. et al. (1995) Low-dose ovine corticotropin-releasing hormone stimulation test in diabetes mellitus with or without neuropathy. Metabolism, 54, 538–542.

Diagnostic and Statistical Manual of Mental Disorders (1994) 4th Edition. American Psychiatric Association, Washington DC.

Distiller, L.A., Sagel, J., Morley, J.E. et al. (1975). Pituitary responsiveness to luteinizing hormone releasing hormone on insulin-dependent diabetes mellitus. Diabetes, 24, 378–380.[Abstract]

Djursing, H., Nyholm, H.C., Hagen, C. et al. (1982) Clinical and hormonal characteristics in women with anovulation and insulin-treated diebetes mellitus. Am. J. Obstet. Gynecol., 143, 876–882.[ISI][Medline]

Djursing, H., Hagen, C., Nyholm, H.C. et al. (1983) Gonadotropin responses to gonadotropin-releasing hormone and prolactin responses to thyrotropin-releasing hormone and metoclopramide in women with amenorrhea and insulin-treated diabetes mellitus. J. Clin. Endocrinol. Metab., 56, 1016–1021.[Abstract]

Djursing, H., Carstensen, L., Hagen, C. et al. (1984) Possible altered dopaminergic modulation of pituitary function in normal-menstruating women with insulin dependent diabetes mellitus (IDDM). Acta Endocrinol. (Copenh.), 107, 450–455.[Medline]

Djursing, H., Andersen, A.N., Hagen, C. et al. (1985) Gonadotropin secretion before and during acute and chronic dopamine-receptor blockade in insulin-dependent diabetic patients with amenorrhea. Fertil. Steril., 44, 49–55.[ISI][Medline]

Erickson, G.F., Garzo, V.G. and Magoffin, D.A. (1989) Insulin-like growth factor-I regulates aromatase activity in human granulosa luteal cells. J. Clin. Endocrinol. Metab., 69, 716–722.[Abstract]

Ghizzoni, L., Vanelli, M., Virdis, R. et al. (1993) Adrenal steroids and adrenocorticotropin responses to human corticotropin-releasing hormone stimulation test in adolescents with type I diabetes mellitus. Metabolism, 42, 1141–1145.[ISI][Medline]

Grossman, A., Moult, P.J.A. and McIntyre, H. (1982) Opiate mediation of amenorrhea in hyperprolactinemia and in weight loss mediated amenorrhea. Clin. Endocrinol., 17, 379–385.[ISI][Medline]

Hanaire-Broutin, H., Sallerin-Caute, B., Poncet, M.F. et al. (1996) Insulin therapy and GH-IGF-1 axis disorders in diabetes: impact of glycaemic control and hepatic insulinization. Diabetes Metab., 22, 245–250.[ISI][Medline]

Iranmesh, A., Veldhuis, J.D., Carlsen, E.C. et al. (1990) Attenuated pulsatile release of prolactin in men with insulin-dependent diabetes mellitus. J. Clin. Endocrinol. Metab., 71, 73–78.[Abstract]

Khushdev, K.K. and Goldsmith, P.C. (1989) Corticotropin-releasing factor neurons innervate dopamine neurons in the periventricular hypothalamus of juvenile macaques. Neuroendocrinology, 50, 351–358.[ISI][Medline]

Kiaer, K., Hagen, C., Sando, S.H. and Eshoj, O. (1992) Epidemiology of menarche and menstrual disturbences in an unselected group of women with insulin-dependent diabetes mellitus compared to controls. J. Clin. Endocrinol. Metab., 75, 524–529.[Abstract]

Nappi, R.E., Petraglia, F., Genazzani, A.D. et al. (1993) Hypothalamic amenorrhea: evidence for a central derangement of hypothalamic–pituitary–adrenal cortex axis activity. Fertil. Steril., 59, 571–576.[ISI][Medline]

Nestler, J.E. and Jakubowicz, D.J. (1996) Decreases in ovarian cytochrome P450 c 17 alpha activity and serum free testosterone after reduction of insulin secretion in polycystic ovary syndrome. N. Engl. J. Med., 335, 617–623.[Abstract/Free Full Text]

O'Hare, J.A., Eichold, B.H. and Vignati, L. (1987) Hypogonadotropic secondary amenorrhea in diabetes: effects of central opiate blockade and improved metabolic control. Am. J. Med., 83, 1080–1084.[ISI][Medline]

Olster, D.H. and Ferin, M. (1987) Cortcotropin releasing-hormone inhibits gonadotropin secretion in the ovariectomized rhesus monkey. J. Clin. Endocrinol. Metab., 65, 262–267.[Abstract]

Ono, N., Lumpkin, M.D., Sampson, W.K. et al. (1984) Intrahypothalamic action of corticotropin-releasing factor (CRF) to inhibit growth hormone and LH release in the rat. Life Sci., 35, 1117–1123.[ISI][Medline]

Poretsky, L. and Kalin, M.F. (1987) The gonadotropic function of insulin. Endocr. Rev., 8, 132–145.[Abstract]

Radetti, G., Paganini, C., Gentili, L. et al. (1994) Altered adrenal and thyroid function in children with insulin-dependent diabetes mellitus. Acta Diabetol., 31, 138–140.[ISI][Medline]

Rivier, C., Rivier, J. and Vale, W. (1986) Stress-induced inhibition of reproductive functions: role of endogenous corticotropin-releasing factor. Science, 231, 607–609.[ISI][Medline]

South, S.A., Asplin, C.M., Carlsen, E.C. et al. (1993) Alterations in luteinizing hormone secretory activity in women with insulin-dependent diabetes mellitus and secondary amenorrhea. J. Clin. Endocrinol. Metab., 76, 1048–1053.[Abstract]

Wurzburger, M.I., Prelevic, G.M., Sonksen, P.H. et al. (1990) The effects of improved blood glucose on growth hormone and cortisol secretion in insulin-dependent diabetes mellitus. Clin. Endocrinol., 32, 787–797.[ISI][Medline]

Xiao, E., Luckahans, J., Niemann, W. et al. (1989) Acute inhibition of gonadotropin secretion by corticotropin-releasing-hormone in the primate: are the adrenal glands involved? Endocrinology, 124, 1632–1637.[Abstract]

Submitted on May 11, 1998; accepted on October 16, 1998.