Insulin binding to human ovaries

The ovarian insulin and insulin-like growth factor system with an emphasis on domestic animals

Insulin and insulin-like growth factors (IGFs) have direct effects on cultured ovarian cells. These effects include stimulation of granulosa cell mitogenesis, granulosa and luteal cell progesterone production, and thecal cell androgen production and appear similar among species. However, species differences exist with regard to insulin and IGF-I effects on granulosa cell estradiol production. In addition to endocrine effects of insulin and IGFs, IGFs are produced by granulosa, thecal, and luteal cells, allowing for an intraovarian autocrine and paracrine system. Granulosa, thecal, and luteal cells contain receptors for insulin and IGFs, and these receptors appear to mediate the effects of insulin and IGFs. Adding to the complexity of the regulatory role of IGFs is the presence of IGF-binding proteins (IGFBPs) within the ovary. These IGFBPs are produced by granulosa, thecal, and luteal cells, and their production is hormonally regulated. Evidence for a coherent mechanism by which insulin, IGFs, and IGFBPs interact and regulate ovarian function in vivo has yet to be found.

Menstrual irregularities are more common in adolescents with type 1 diabetes: association with poor glycaemic control and weight gain

Ovarian function in post-menarchal girls with Type 1 diabetes was evaluated. Menstrual histories from 24 adolescents with Type 1 diabetes were compared with those from 24 age and sex matched controls. A fasting blood sample was obtained from subjects with Type 1 diabetes for the measurement of ovarian and adrenal sex hormones, LH and FSH, glucose and insulin, insulin-like growth factor-I (IGF-I), and insulin-like growth factor binding protein-1 (IGFBP-1); and an ovarian ultrasound scan was performed. Menstrual irregularity was more prevalent in patients with Type 1 diabetes than controls (54% vs 21%, p < 0.01) and their mean body mass index (BMI) was greater (22.3 +/- 0.5 (+/- SEM) vs 20.7 +/- 0.6 kg m-2, p < 0.05). Subjects with Type 1 diabetes with irregular menses (when compared with diabetic subjects with a regular cycle) had a significantly higher HbA1 (12.8 +/- 0.4 vs 10.5 +/- 0.5%, p < 0.01) and BMI (23.2 +/- 0.6 vs 21.4 +/- 0.6 kg m-2, p < 0.05) associated with a lower sex hormone binding globulin (SHBG) (37.2 +/- 4.0 vs 52.6 +/- 4.0 nmol l-1, p < 0.025) and IGF-I (1.4 +/- 0.2 vs 2.2 +/- 0.2 mUI-1, p < 0.025) and a higher LH:FSH ratio (2.6 +/- 0.5 vs 1.4 +/- 0.2, p < 0.05). Polycystic ovarian changes were identified in 10/13 (77%) of these patients with an irregular cycle. Menstrual irregularity is common in post-menarchal girls with Type 1 diabetes and is associated with poor glycaemic control and weight gain. The apparent high incidence of polycystic ovarian change requires further investigation.

Medical therapy for the syndrome of familial virilization, insulin resistance, and acanthosis nigricans

In the syndrome of familial virilization, insulin resistance, and acanthosis nigricans, the interrelationships are not understood. Twin sisters were studied, along with a lesser affected sister and mother. They manifested amenorrhea, hirsutism, masculinization, hypertension, hyperinsulinemia, hypertriglyceridemia, and hyperprolactinemia. Medical therapy with a gonadotropin-releasing hormone agonist plus an antiandrogen resulted in reversal of the hirsutism, yet with preservation of potential fertility. In response to luteinizing hormone (LH) and follicle-stimulating hormone suppression, there was normalization of the serum androgens, but not of the hyperinsulinemia, hypertriglyceridemia, hyperprolactinemia, hypertension, or acanthosis nigricans.

CONCLUSIONS

(1) This syndrome may be familial. (2) Medical therapy for the virilization is successful. (3) The hyperandrogenemia is primarily LH dependent and not primarily insulin dependent, although insulin may have an amplification effect. (4) Hyperinsulinemia, hypertriglyceridemia, hyperprolactinemia, and the hypertension are not androgen dependent.

Determination of insulin and insulin-like growth factors in the ovarian circulation

Recent in vitro studies implicate the ovary as an extra-hepatic source of insulin-like growth factors (IGFs) with production regulated by gonadotropins and local steroids. Because previous studies have failed to show any significant variations in IGF levels in peripheral blood during the menstrual cycle, we measured the concentrations of IGF-I, IGF-II, and insulin in ovarian and peripheral venous blood samples obtained simultaneously from nine women undergoing abdominal hysterectomy to obtain more detailed data on the ovarian contribution. A significant decreased ovarian gradient was found for IGF-II but not for IGF-I or insulin. Although there was no significant ovarian vein insulin gradient, insulin levels were higher in follicular than in luteal phase ovarian samples. These data suggest that IGF-II may be locally regulated by the ovary. Both insulin and IGFs may regulate ovarian function in vivo.

Alterations in carbohydrate metabolism as they apply to reproductive endocrinology

This review has characterized the current state of knowledge of four clinical situations in which an interrelationship of gynecology, endocrinology and carbohydrate metabolism is recognized. The literature contains conflicting descriptions of changes in glucose homeostasis during the menstrual cycle and while using birth control pills. Physiologic changes in receptor number have been demonstrated in each of these situations, so failure to observe differences using glucose tolerance testing may reflect an in vivo homeostatic response to changes in these hormone levels. Thus, in vivo identification of alterations in carbohydrate metabolism induced by endogenous or exogenous steroids may require utilization of models that prevent these homeostatic mechanisms. The association between hyperandrogenism and hyperinsulinism has been better characterized, but the relationship is complicated by the frequent coexistence of obesity. The association may be due to insulin-stimulated ovarian androgen production, and insulin insensitivity may reflect a postreceptor defect. Insulin and its metabolic effects have also been implicated in ovulatory dysfunction in women with diabetes mellitus and identified as a factor affecting all levels of the hypothalamic-pituitary-ovarian axis. A clearer understanding of these relationships and their application to clinical management await further study.

Insulin as a factor of increased androgen production in women with obesity and polycystic ovaries

To evaluate the possible role of moderate hyperinsulinemia on abnormal androgen secretion, we examined 4 age and weight-matched groups of obese subjects: 2 groups of women with normal menses whose fasting insulin (IRI) levels were less than or equal to 20 microU/ml (OB-I) or greater than or equal to 40 microU/ml (OB-I) and 2 groups of women with polycystic ovaries who were similarly grouped. All subjects underwent an oral glucose tolerance test, blood sex hormone determination and multiple LH determinations. Compared to OB, OB-PCO women showed significantly higher values of LH, androgen and estrogen concentrations. OB-I and OB-II showed similar hormonal patterns. On the contrary, OB-PCO-II presented significantly (p less than 0.05) higher androstenedione concentrations (348.7 +/- 129.9 ng/dl) (m +/- SD) than OB-PCO-I women (237.0 +/- 73.7 ng/dl). These differences were evident despite similar plasma LH concentrations. In conclusion, these results suggest that insulin may be a factor amplifying LH-dependent androgen secretion in hyperandrogenized women with obesity and PCO.

Spectrum of endocrine abnormalities associated with acanthosis nigricans

Acanthosis nigricans is a marker for disorders of insulin action, endocrine abnormalities, and cancer of internal organs. To evaluate the clinical significance of this marker the systemic alterations and clinical features of 26 patients with acanthosis nigricans seen at two institutions were reviewed. Most subjects affected by acanthosis nigricans were female (20 patients), Caucasian (22 patients), in the third decade of life (13 patients), and overweight (24 patients greater than 120 percent ideal body weight). Gonadal disease, present in 17 patients, was expressed as polycystic ovary syndrome (11 cases), disorders of prolactin secretion (two cases, one with polycystic ovary syndrome), streak gonads (one case), and hypogonadism of the male (four cases). Thyroid disease and tinea versicolor were present in four patients each. Three patients were receiving insulin therapy for diabetes mellitus, and in two additional patients diabetes mellitus was detected during the diagnostic workup. All patients had elevated fasting insulin levels; most of them also had an exaggerated insulin response to a glucose load. Two of 18 patients tested had antibodies against the insulin receptor in the circulation. Skin biopsy of acanthosis nigricans lesions from all 26 patients showed a typical pattern of hyperkeratosis, acanthosis, and epidermal papillomatosis. Colloidal iron staining showed glycosaminoglycan infiltration of the papillary dermis (21 of 21 cases), consisting mainly of hyaluronic acid. It is concluded that: (1) hyperinsulinenemia and local dermal glycosaminoglycan deposition are regular features in acanthosis nigricans and (2) patients with acanthosis nigricans should be screened for diabetes mellitus, gonadal disease, and hypothyroidism.

Sex hormones in obese premenopausal women and their relationships to body fat mass and distribution, B cell function and diet composition

We examined sex hormone blood concentrations in a group of 33 obese non-hirsute premenopausal women with normal menses and in 14 age-matched normal-weight controls, and evaluated their relationship with anthropometric parameters, dietary habits and insulin levels. Obese women showed lower than control sex hormone-binding globulin (24.9 +/- 14.6 vs 38.6 +/- 12.5 nmol/l; p less than 0.005) and 5 alpha-dihydrotestosterone (13.7 +/- 5.4 vs 18.2 +/- 4.8 ng/dl; p less than 0.005) values. Despite their consensual behavior, the correlation coefficient between 5 alpha-dihydrotestosterone and sex hormone-binding globulin was not significant in the obese while in controls it was 0.68 (p less than 0.01). This suggests that mechanisms operating to lower the plasma levels of these compounds may be regulated differently in obesity. Body Mass Index, per cent body fat and its distribution showed a highly significant negative correlation with sex-hormone binding-globulin and 5 alpha-dihydrotestosterone values. Insulin levels did not appear to be correlated with sex hormone values. On the contrary, in the obese women we found a highly significant correlation between dietary lipids and sex-hormone-binding-globulin levels (r = -0.54; p less than 0.005) and between dietary carbohydrates and estrone values (r = 0.47; p less than 0.005); all these relationships were independent of body weight. These results confirm that in premenopausal women obesity may be characterized by detectable changes in sex steroid metabolism and suggest a possible causal role not only of the excessive quantity of metabolically active adipose tissue but also of specific dietary factors.

Elevated serum dehydroepiandrosterone sulfate levels in patients with insulin resistance, hirsutism, and acanthosis nigricans

The association of insulin resistance, hyperandrogenism, and acanthosis nigricans is well established. The ovary is thought to be the site of the excess androgen production. The purpose of this study was to assess the adrenal contribution to the hyperandrogenic state in these women. Twenty-three patients presenting with the combination of hyperinsulinemia, elevated testosterone (T) levels, and acanthosis nigricans were investigated for the source of the increased androgen production. Twelve patients had elevated serum dehydroepiandrosterone sulfate (DS) levels (high DS group) suggestive of increased adrenal androgen production. Eleven patients had normal DS levels (normal DS group). Both normal DS and high DS groups had similar basal serum insulin levels and similar insulin response curves after a 3-hour, 75-gm, oral glucose tolerance test. No correlation was found between serum T or DS levels and either basal serum insulin levels or the area under the insulin response curve. These data suggest that DS levels are frequently elevated in patients with hirsutism, acanthosis, and hyperinsulinemia. Furthermore, the lack of association between serum DS and serum insulin levels suggests that insulin does not directly affect adrenal androgen production, or vice versa.

Effect of weight loss and antiandrogenic therapy on sex hormone blood levels and insulin resistance in obese patients with polycystic ovaries

This study was performed in two randomly defined groups of obese patients with polycystic ovaries to investigate the overall effects of hypocaloric diet combined (group 2) or not combined (group 1) with an antiandrogenic therapy (cyproterone acetate, 50 mg/day, plus ethinyl estradiol, 0.05 mg/day) on sex hormone plasma levels, insulin secretion and resistance, and body weight loss and on their reciprocal interrelationships. All obese patients with polycystic ovaries showed elevated luteinizing hormone and androgen levels, hyperinsulinemia, and marked insulin resistance. After an average period of 3 months both groups showed a similar weight loss and a similar reduction in the insulin-resistant state. During treatment in group 1 three patients had a greater frequency of menstrual bleeding, and in one of them an ovulatory cycle was documented. Whereas, no changes in gonadotropin and sex steroid levels were found in group 1, a significant fall was observed in group 2. No relationships were observed between these changes and those which occurred on insulin levels. We conclude that hyperandrogenism in obese patients with polycystic ovaries does not appear to be a primary factor leading to the insulin-resistant state.

Obesity, acanthosis nigricans, insulin resistance, and hyperandrogenemia: pediatric perspective and natural history

We studied the syndrome of acanthosis nigricans, obesity, insulin resistance, and hyperandrogenemia in 22 patients. Although isolated case reports in adolescents have appeared, this syndrome has not received full recognition as a pediatric entity. Our patients (17 girls, five boys) had a mean weight 5.7 SD above the mean for age, although mean height was only 0.5 SD above the mean for age. All patients had acanthosis nigricans. Their insulin resistance was significantly greater than that in a control group with comparable obesity. Fasting insulin concentration was 5.25 microU/ml in lean controls, 19.6 microU/ml in obese controls, and 49.8 microU/ml in study patients (P less than 0.002). Mean glucose disappearance rate during an insulin tolerance test was 6.7%/min in lean controls, 5.19%/min in obese controls, and 2.35%/min in study patients (P less than 0.02). After menarche, mean plasma testosterone concentration was 106 ng/dl, compared with less than 50 ng/dl in all lean and obese control patients. Data derived from our series of patients lead us to conclude that (1) this is a genetic syndrome, although the exact mode of inheritance is unclear; (2) the natural history of the syndrome invariably begins with the onset of obesity, followed by acanthosis nigricans that worsens with progressive weight gain; (3) acanthosis nigricans is thus a marker for hyperinsulinemia, which occurs before hyperandrogenemia; (4) hyperandrogenemia occurs only after menarche. Identification of this syndrome should permit monitoring for the development of hyperandrogenemia during puberty and determination of other affected family members.

In vitro binding of insulin and epidermal growth factor to human endometrium and endocervix

The distribution of receptors for insulin and epidermal growth factor along the longitudinal axis of the uterine cavity was studied in 28 uteri obtained from women of reproductive age undergoing hysterectomy for benign conditions. Insulin binding to crude plasma membranes was higher (p less than 0.05) in the secretory than in the proliferative phase of the menstrual cycle in all uterine segments (fundus to cervix). Epidermal growth factor binding did not change during the menstrual cycle but the number of epidermal growth factor binding sites was higher in the cervix than in the fundus (p less than 0.05). Scatchard plots of binding data, obtained with crude plasma membranes from pooled uteri, were curvilinear; the high-affinity sites had dissociation constants of 1 to 4 nmol/L and receptor concentrations of 100 to 300 fmol/mg of protein, for both iodine 125-labeled insulin and 125I-labeled epidermal growth factor. In plasma membranes, obtained from another 15 uteri, mouse nerve growth factor (3.3 micrograms/ml) decreased the binding of insulin by an average of 17% (p less than 0.005); in the decidua of a pregnant uterus at 12 weeks Scatchard analysis showed that nerve growth factor decreased the affinity but not the number of insulin-binding sites. Nerve growth factor had no effect on epidermal growth factor binding. Human prolactin (2 micrograms/ml) also decreased insulin binding by an average of 18% (n = 5, p less than 0.025) but had no effect on epidermal growth factor binding. These "baseline" data will be useful in further studies of the possible interactions between (1) receptors for various peptide growth factors and (2) sex steroid hormones, in normal and neoplastic endometrium and cervix.