Endocrine Abstracts

Introduction: Obesity increases the incidence of hypogonadism in men, and hypogonadism in turn plays a role in obesity. One of the first mechanisms proposed to explain this was a hypothesis based on the principle that obese men have higher estrogen levels, and that increased estrogens provide feedback to the hypothalamic-pituitary-testicular axis, reducing the secretion of gonadotropins and leading to a decrease of overall testosterone levels. This concept has since been questioned, though never completely disproven.

Methods: A total of 224 healthy men (except for their obesity) aged 20 to 78 with a broad range of body mass index (BMI) from 18 to 39 were enrolled in the study. All patients signed informed consent forms before taking part in the study. Blood withdrawal and anthropomorphic data were obtained from fasting subjects in the morning between 7:30 and 8:30 am. Serum total testosterone and estradiol were determined by radioimmunoassay. SHBG, lutropin and follitropin were measured using immunoradiometric assay. Moreover, we have calculated free testosterone. The men were then divided into three subgroups according to BMI. The first subgroup consisted of 109 men with BMI between 18 and 25 (normal weight men), the second group included 78 men with BMI between 25 and 30 (considered overweight), and the third subgroup had 37 men with BMI 30 to 39 (considered obese). We compared hormone levels betwen groups.

Results: The differences in estradiol levels between the groups were not significant. Though there was a relative increase of 10% in the levels of estradiol in obese men compared to normal weight men. In the overweight group there was even a decrease compared to normal weight men. In comparison with normal weight men, obese and overweight patients had significantly lower levels of total testosterone and higher SHBG, and in consequence the free androgen index. Total testosterone differed significantly between overweight and obese men, whereas SHBG differed significantly between normal weight men and overweight men, but not between overweight and obese men. Levels of FSH and LH showed no significant differences among the groups, though there was a slight tendency toward higher levels in obese men.

Conclusion: Our findings are in line with the idea that estrogen production in overweight and obese men with BMI up to 39 kg/m² does not significantly influence endocrine testicular function.

Acknowledgments: The study was supported by the project MHCZ-DRO (Institute of Endocrinology-EÚ, 00023761).