Role of growth hormone in polycystic ovarian syndrome

Insulin and Growth Hormone Balance: Implications for Obesity

Disruption of endocrine hormonal balance (i.e., increased levels of insulin, and reduced levels of growth hormone, GH) often occurs in pre-obesity and obesity. Using distinct intracellular signaling pathways to control cell and body metabolism, GH and insulin also regulate each other's secretion to maintain overall metabolic homeostasis. Therefore, a comprehensive understanding of insulin and GH balance is essential for understanding endocrine hormonal contributions to energy storage and utilization. In this review we summarize the actions of, and interactions between, insulin and GH at the cellular level, and highlight the association between the insulin/GH ratio and energy metabolism, as well as fat accumulation. Use of the [insulin]:[GH] ratio as a biomarker for predicting the development of obesity is proposed.

Effect of pioglitazone on glucose metabolism and luteinizing hormone secretion in women with polycystic ovary syndrome

OBJECTIVE

To thoroughly examine the mechanisms for insulin resistance in polycystic ovary syndrome (PCOS) and to evaluate the effects of pioglitazone treatment on insulin resistance, beta-cell function, LH secretion, and glucose metabolism.

DESIGN

Randomized, blinded, placebo-controlled study.

SETTING

Outpatient clinic, at a university hospital in Denmark.

PATIENT(S)

Thirty obese women with PCOS and 14 weight-matched healthy females.

INTERVENTION(S)

Sixteen weeks of blinded treatment with pioglitazone (30 mg/d) or placebo.

MAIN OUTCOME MEASURE(S)

Fasting blood samples, 24-hour 20-minute integrated blood sampling (LH, insulin, and C-peptide), euglycemic hyperinsulinemic clamps including 3-(3)H glucose, and indirect calorimetry were performed before and after the intervention period.

RESULT(S)

Patients with PCOS had significantly lower insulin sensitivity compared with controls, including significantly decreased insulin-stimulated oxidative and nonoxidative glucose metabolism. Pioglitazone treatment resulted in significantly lower levels of fasting insulin and significantly higher insulin sensitivity, increased insulin-stimulated glucose oxidation, and increased insulin-stimulated inhibition of lipid oxidation. During 24-hour blood sampling, significantly lower area under-the-curve insulin and lower median insulin levels were observed. Secretion profiles of LH and E(2) and T levels did not change significantly.

CONCLUSION(S)

Insulin resistance in PCOS was characterized by hyperinsulinemia, impaired insulin-stimulated oxidative and nonoxidative glucose metabolism, which was partly reversed by pioglitazone treatment.

Growth-hormone response to combined stimulation with GHRH plus GH-releasing peptide-6 in obese patients with polycystic ovary syndrome before and after short-term fasting

Controversial data were reported on GH response to different provocative stimuli in obese patients with polycystic ovary syndrome (PCOS). The objective of our study was to assess the effect of short-term fasting on GH response to combined stimulus with GHRH+GH-releasing peptide-6 (GHRP-6) in obese patients with PCOS and possible relation with leptin and insulin changes during fasting. Twelve obese PCOS women and nine obese control women participated in 3-day fasting. GH response, IGF-I, insulin and leptin were measured after GHRH+ GHRP-6, before and after short-term fasting. Obese PCOS patients had significantly greater GH peak after GHRH+GHRP-6 before fasting. Enhanced response to GH stimulation was found after fasting without substantial differences between obese PCOS and obese controls. Insulin and leptin significantly decreased, while insulin sensitivity significantly improved in both groups during fasting. In conclusion, obese PCOS patients have peculiar type of GH response to GHRH+GHRP-6 before fasting, possibly due to enhanced sensitivity of somatotrophs. Observed changes in insulin and leptin may participate in modulation of enhanced GH response after short-term fasting to GHRH+GHRP-6 in PCOS and obese controls.

Polycystic Ovary Syndrome in Adolescents

Polycystic ovary syndrome is a heterogeneous clinical syndrome, which has been defined as the association of hyperandrogenism with chronic anovulation in women without specific adrenal and pituitary gland disease. A family history of polycystic ovary syndrome may be present in a subset of patients; however, the genetic basis of the syndrome remains unclear. Most often, the age of onset is perimenarchal and it is characterized by the appearance of menstrual disturbances, hirsutism, acne, and more rarely, a male pattern of alopecia. In some cases, premature adrenarche may present as a precursor to the development of the syndrome. Polycystic ovary syndrome is also associated with metabolic disturbances, such as obesity and insulin resistance with hyperinsulinemia, for which the pathophysiological role in the development of the syndrome has been recognized. The therapeutic approaches to polycystic ovary syndrome include lifestyle modifications, dietary-induced weight loss, insulin-sensitizing agents, antiandrogens, and oral contraceptives. These treatments may improve the clinical manifestations of excess androgen production and normalize menses in many adolescents and young women with polycystic ovary syndrome. Early recognition of the syndrome and thus, early treatment, may prevent and possibly ameliorate all the symptoms and the potential later development of metabolic and cardiovascular complications.

Involvement of growth factors in the pathophysiology of polycystic ovary syndrome

The etiology of polycystic ovary syndrome (PCOS) has not yet been fully elucidated but involves a disruption of normal ovarian function and multisystem sequelae. A combination of abnormally functioning genes whose expression is influenced by environmental, extra-ovarian factors determines the symptoms. Growth factors are heavily involved in the pathophysiology, either contributing to or as a consequence of the arrested development of follicles, abnormal steroidogenesis and hyperinsulinemia. Hyperactivity of a--transforming growth factor (TGFa) and epidermal growth factor (EGF) may block stimulation of aromatase and attenuate apoptosis of follicles and other factors may interface with the insulin-like growth factor (IGF) system preventing arrested follicles from becoming atretic and preventing the selection of a dominant follicle. IGF-binding protein concentrations are decreased by insulin, freeing biologically active IGF-I which augments the action of luteinizing hormone (LH) by inducing LH receptors, hyperactivating the enzymes P450c17a and 17,20 lyase resulting in hyperandrogenism. Growth hormone itself may be involved in the pathophysiology, as in normoinsulinemic PCOS patients it is hypersecreted and its actions on growth factors and their binding proteins are similar to those of insulin.