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Key words: AGE GROUP, AGING MALE, GONADOTROPIN, INHIBIN B, TESTOSTERONE DECLINE
ABSTRACT
The decline of testosterone levels in aging men is well documented. However, it is unclear to what extent the Sertoli cell marker inhibin B changes during aging. Herein we report on the determination of serum levels of inhibin B, follicle stimulating hormone (FSH), luteinizing hormone (LH) and testosterone in 906 patients from 16 to 89 years of age, presenting to our department for different complaints. There was a weak but significant correlation of the levels of inhibin B with age (r = 0.064, p < 0.05). A significant negative
correlation of FSH and inhibin B was documented in all age groups (r = -0.423, p < 0.01). Also, the LH levels increased significantly with low inhibin B levels (r = -0.289, p < 0.01). Testosterone levels showed no significant correlation with inhibin B. We conclude from our study that Sertoli cell function as documented by serum levels of inhibin B is stable throughout life. In addition, the ongoing correlation of FSH and inhibin levels also indicates no significant decline of Sertoli cell function in the aging male.
INTRODUCTION
Follicle stimulating hormone (FSH) levels increase with age in the male. Testosterone levels in aging men decline slowly but continuously, beginning with the 40th year of life1. However, this decline is not accompanied by a similar decrease of spermatogenic activity, although this also shows some alteration with age2. This suggests that Sertoli cell function is maintained in the aging man.
The Sertoli cells of the testis produce inhibin B. Therefore, serum levels of inhibin B are a marker of Sertoli cell function3. Inhibin B secretion is under the control of FSH, and vice versa. As a consequence, serum levels of these two hormones are inversely correlated4.
After orchiectomy men have undetectably low levels of inhibin B, while those with Klinefelter's syndrome and untreated idiopathic hypogonadotropic hypogonadism (IHH) have detectable levels. Men with otherwise defective tubular function have significantly lower levels than normal men. For cryptorchid men, the mean inhibin B levels are lower than those of control men. Low levels of inhibin B among individuals are an indication of diminished semen production5.
Since Sertoli cells support spermatogenic activity, a marker of...