Patients with polycystic ovary syndrome (PCOS) had significantly higher levels of total insulin-like growth factor (IGF-I) than those in age- and weight-matched controls (PCOS, 230 ± 21 ng/ml; control, 180 ± 16 ng/ml; mean ± SE, p < 0.05) as well as free IGF-I (PCOS, 3.8 ± 0.2 ng/ml; control, 3.0 ± 0.2 ng/ml; p < 0.05). These elevated levels of IGF-I were correlated slightly with levels of LH and LH/FSH ratio (r = 0.171, p < 0.05 and r = 0.239, p < 0.01, respectively). Elevated fasting levels of insulin and decreased levels of IGF binding protein (32K-BP) were also observed in PCOS, and the levels of 32K-BP in PCOS were negatively correlated with insulin (r = -0.39, p < 0.01). These results suggest that elevated IGF-I levels and decreased 32K-BP levels in the circulation are one of the endocrinological features of PCOS and that insulin is responsible for the clinical manifestation of decreased 32K-BP levels in PCOS.

The pineal hormone melatonin (N-acetyl-5-methoxytryptamine) exerts antigonadotropic effects in some mammalian species. To evaluate the effect of luteinizing hormone (LH) on melatonin release and its synthesizing enzyme activities in pineal glands, pineals of adult female rats undergoing diestrus were organ-cultured in a medium containing 10(-12), 10(-10) or 10(-8) M LH for 6 h. Melatonin release increased significantly in pineals cultured with 10(-12) and 10(-10) M LH, as compared to control values. Similarly, the activity of arylalkylamine N-acetyltransferase (NAT), the key regulatory enzyme in melatonin biosynthesis, was significantly higher in pineals cultured with 10(-12) and 10(-10) M LH for 6 h, while LH at 10(-8) M had no effect. Although LH at 10(-10) M increased pineal hydroxyindole-O-methyltransferase (HIOMT) activity, which catalyzes the final step of melatonin biosynthesis, LH at 10(-12) and 10(-8) M had no effect. These results demonstrate that at relatively low physiological levels, LH stimulates pineal melatonin synthesis and release, mainly by increasing NAT activity.

To evaluate the effect of gonadotropin-releasing hormone (GnRH) on melatonin ( N-acetyl-5-methoxytryptamine) release and its synthesizing enzyme activities in pineal glands, pineals from adult female rats during diestrus were organ-cultured in a medium containing 10 -12, 10 -10, or 10 -8 M GnRH for 6 h. Melatonin release increased significantly in pineals cultured with 10 -10 and 10 -8 M GnRH compared to controls. However, in pineal glands that were organ-cultured in a medium containing 10 -12 to 10 -8 M GnRH, the activity of arylalkylamine N-acetyltransferase, which is the key regulatory enzyme in melatonin biosynthesis, showed no significant difference from controls. Likewise, GnRH at these concentrations had no significant effect on the activity of pineal hydroxyindole- O-methyltransferase, which catalyzes the final step of melatonin biosynthesis. These results show that GnRH stimulates pineal melatonin release, but suggest that GnRH does not affect its melatonin synthesis.

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