Endocrine Abstracts (2006) 11 P337

Testosterone secretion and melatonin rhythm in men with the metabolic syndrome

R Robeva, G Kirilov & Ph Kumanov

Sbaleng, Sofia, Bulgaria.

Introduction: Low endogenous testosterone levels are related to the metabolic syndrome /MS/ and diabetes type 2 in middle-aged and elderly men, but little is known about interrelations testosterone-insulin in younger hyperinsulinemic men. Recent studies have shown that the night melatonin in males with hypogonadotropic hypogonadism is significantly higher in comparison with the healthy men, while it is significantly reduced in patients with hypergonadotropic hypogonadism. However, it’s still not clear whether the melatonin rhythm is changed in cases of low normal testosterone levels or mild hypogonadism.

Objectives: To compare the testosterone levels in young (within the reproductive age) men with MS to healthy controls and to investigate the possible changes in their melatonin rhythm.

Subjects and methods: BMI, HOMA-IR, serum lipids, fasting insulin and testosterone were investigated in 22 age-matched men (mean age 31.00±2.42 years) (at 8 h): 11 healthy controls (HC) and 11 men with metabolic syndrome (MSP). Melatonin and LH were measured at 19 h, 03 h and 11 h.

Results: A significant difference was found between the testosterone levels in HC (21.1±2.17) and MSP (11.88±1.09), P=0.001. Testosterone levels correlated significantly with fasting insulin (r=−0.521; P=0.015), HOMA-IR (r=−0.516; P=0.017) and BMI (r=−0.549; P=0.008). No changes in the melatonin rhythm of the two groups were found. LH levels in both groups were similar, however a tendency to higher night LH levels in MS patients was observed (LH /HC) =3.51±0.46; (LH /MS) =5.17±0.68; P=0.057.

Conclusion: Endogenous testosterone levels are significantly lower in young men with metabolic syndrome compared to healthy age-matched controls. The mild hypogonadism in hyperinsulinemic patients is not related with changes in melatonin rhythm, suggesting that factors different from the testosterone are responsible for the melatonin fluctuations by hypo- and hypergonadotropic hypogonadism.

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