Effect of feeding on growth hormone response to growth hormone-releasing hormone in polycystic ovarian syndrome: relation with body weight and hyperinsulinism

Oxidative Stress and Low-Grade Inflammation in Polycystic Ovary Syndrome: Controversies and New Insights

The pathophysiology of Polycystic Ovary Syndrome (PCOS) is quite complex and different mechanisms could contribute to hyperandrogenism and anovulation, which are the main features of the syndrome. Obesity and insulin-resistance are claimed as the principal factors contributing to the clinical presentation; in normal weight PCOS either, increased visceral adipose tissue has been described. However, their role is still debated, as debated are the biochemical markers linked to obesity per se. Oxidative stress (OS) and low-grade inflammation (LGI) have recently been a matter of researcher attention; they can influence each other in a reciprocal vicious cycle. In this review, we summarize the main mechanism of radical generation and the link with LGI. Furthermore, we discuss papers in favor or against the role of obesity as the first pathogenetic factor, and show how OS itself, on the contrary, can induce obesity and insulin resistance; in particular, the role of GH-IGF-1 axis is highlighted. Finally, the possible consequences on vitamin D synthesis and activation on the immune system are briefly discussed. This review intends to underline the key role of oxidative stress and low-grade inflammation in the physiopathology of PCOS, they can cause or worsen obesity, insulin-resistance, vitamin D deficiency, and immune dyscrasia, suggesting an inverse interaction to what is usually considered.

Administration of exogenous ghrelin in obese patients with polycystic ovary syndrome: effects on plasma levels of growth hormone, glucose, and insulin

OBJECTIVE

To assess the effects of the administration of exogenous ghrelin, a peptide with potent GH-releasing activity and glucose-enhancing and insulin-lowering properties, in obese patients with polycystic ovary syndrome (PCOS).

DESIGN

Prospective, controlled study.

SETTING

Academic research environment.

PATIENT(S)

Twenty obese women with PCOS, and 15 obese controls.

INTERVENTION(S)

Oral glucose tolerance test (OGTT) and ghrelin test (1 microg/kg i.v. bolus).

MAIN OUTCOME MEASURE(S)

Basal hormonal assays, including ghrelin, were performed. Glucose, insulin, and C-peptide were assessed in a fasting condition and during the OGTT. Growth hormone, insulin, and glucose were measured basally and every 15 minutes for 90 minutes after the injection of ghrelin.

RESULT(S)

Both groups showed an insulin response to the glucose load above the normal range. Significantly lower levels of ghrelin were detected in patients with PCOS compared to controls (108.96 +/- 27.65 Fmol/mL versus 162.47 +/- 42.23 Fmol/mL). Administration of ghrelin markedly enhanced GH levels in both groups (1,888.59 +/- 1,209.53 ng/mL and 1,639.95 +/- 631.79 ng/mL per 90 minutes as GH area under the curve, respectively), with a peak occurring 30 minutes after injection. Ghrelin also induced a trend toward an increase in plasma glucose levels, and a significant decrease in insulin concentrations in both groups.

CONCLUSION(S)

The injection of ghrelin seems to override the GH secretion defect in obese women with PCOS, and to induce glucoinsulinemic changes in both controls and obese patients with PCOS.

Effect of metformin on the growth hormone response to growth hormone–releasing hormone in obese women with polycystic ovary syndrome

OBJECTIVE

Obese women with polycystic ovary syndrome (PCOS) show a marked growth hormone (GH) hyporesponsiveness to several stimuli. We aimed to evaluate the impact of insulin metabolism on the GH secretion impairment in these subjects in relation to food ingestion.

DESIGN

Prospective clinical study.

SETTING

Academic research center.

PATIENT(S)

Nine obese women with PCOS.

INTERVENTION(S)

Metformin (1,500 mg/daily) was administered for three months. The study protocol, which was performed before and after therapy, included hormonal and lipid assays, oral glucose tolerance test (75 g), euglycemic hyperinsulinemic clamp, and growth hormone-releasing hormone (GHRH) test (50 microg/ev), both on fasting and after a standard meal.

MAIN OUTCOME MEASURE(S)

Growth hormone response to GHRH (expressed as the area under the curve) in different experimental conditions.

RESULT(S)

The preprandial GH response to GHRH was not modified by the therapy, whereas a significant increase (P<.05) occurred in the postprandial GH secretion, thus resembling the response of obese normal persons. This change was accompanied by a trend towards improvement, though not statistically significant, of all the evaluated glycoinsulinemic parameters. A significant reduction in cholesterol (P<.01) and androstenedione (P<.05) and an increase in sex hormone-binding globulin (P<.05) were also achieved.

CONCLUSION(S)

These data suggest that metformin is able to affect GH secretion in obese women with PCOS, even with minimal metabolic modifications.

Aspectos neuroendócrinos na síndrome dos ovários policísticos

A síndrome dos ovários policísticos (PCOS) é a endocrinopatia mais freqüente na mulher em idade reprodutiva. O quadro clínico é variável, mas em geral apresenta-se com hirsutismo, acne e/ou alopecia androgênica, anovulação crônica associada a distúrbio menstrual e infertilidade. A resistência insulínica pode estar presente em mais da metade dos casos, em especial nas pacientes obesas. A etiopatogenia ainda não foi totalmente esclarecida, mas mecanismos neuroendócrinos vêm sendo estudados nos últimos anos. Embora esteja bem estabelecida a presença de secreção inapropriada do eixo GnRH-LH em pacientes com PCOS, algumas delas, especialmente as obesas/hiperinsulinêmicas, exibem níveis normais de LH e uma atenuação de sua resposta aos testes de estímulo. Recentemente, descrevemos uma correlação negativa entre leptina e LH em pacientes com PCOS, sugerindo que a atenuação nos níveis de LH nestas pacientes possa estar relacionada a um estado de resistência à leptina. Por outro lado, evidências sugerem que o eixo somatotrófico participe também dos mecanismos fisiopatológicos envolvidos na PCOS. Dados recentes do nosso grupo demonstram que pacientes de peso normal e normoinsulinêmicas apresentam uma maior resposta do GH à clonidina do que pacientes com hirsutismo idiopático. Um mecanismo possível seria uma ação co-gonadotrófica do GH, contribuindo para o hiperandrogenismo clínico e a anovulação. Outra possibilidade é que a elevação da secreção de GH seja somente um epifenômeno vinculado ao aumento de androgênios ovarianos e sua conversão periférica em estrogênios. Estudos futuros são necessários para esclarecer os mecanismos subjacentes associados às alterações descritas neste trabalho e sua relevância na etiopatogenia, diagnóstico e tratamento desta síndrome.

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.

Effect of the opioid blockade on the feeding-induced growth hormone response to growth hormone-releasing hormone in women with polycystic ovary syndrome

OBJECTIVE

To investigate the effect of naloxone, an opioid receptor antagonist, on the release of growth hormone (GH) induced by the growth hormone-releasing hormone (GHRH) in normal-weight and obese women with PCOS in relation to feeding.

DESIGN

Prospective clinical study.

SETTING

Academic research center.

PATIENT(S)

Seventeen women with PCOS (10 who were normal weight and 7 who were obese) and 14 control women (7 who were normal weight and 7 who were obese).

INTERVENTION(S)

A GHRH test (50 microg i.v.) and, on a different day, a GHRH test during a naloxone infusion (1.6 mg/h) during fasting. The same tests were repeated after a standard meal.

MAIN OUTCOME MEASURE(S)

GH response to GHRH (expressed as the area under the curve [AUC]) in different experimental conditions.

RESULT(S)

All normal-weight women showed a significantly higher AUC-GH compared with obese women in the fasting state. Normal-weight controls had a decrease in GH response to GHRH after feeding, and naloxone did not reverse the decrease. In obese controls, feeding increased the GH response but naloxone induced a decrease in the AUC. In fasting, normal-weight women with PCOS, naloxone significantly decreased the AUC-GH; in these patients, food intake induced an inhibition of GH response to GHRH, reversed by naloxone infusion. In obese PCOS patients, GH levels did not increase significantly after GHRH stimulation, either in the fasting state or after a meal, and naloxone did not affect these responses.

CONCLUSION(S)

Factors other than obesity and insulin may be involved in disruption of GH secretion in women with PCOS.