Annual rhythmic variations of follitropin, lutropin, testosterone and sex-hormone-binding globulin in men

The annual rhythmic variations of the serum concentrations of follitropin, lutropin, sex-hormone-binding globulin and testosterone, the ratio between the serum concentrations of testosterone and sex-hormone-binding globulin, and the salivary concentration of testosterone were investigated in a group of 20 apparently healthy men. Venous blood and salivary specimens were collected at 1-month intervals during 12 months. The annual rhythms were studied by using a periodic function resulting from the sum of three cosine functions with periods of 365, 182.5 and 121.66 days. For the salivary concentration of testosterone and for the ratio between the serum concentrations of testosterone and sex-hormone-binding globulin, only the cosine function with a period of 365 days was significant, and for the serum concentration of lutropin, only the cosine function with a period of 121.66 days was significant. Serum concentrations of follitropin, sex-hormone-binding globulin and testosterone were significantly affected by 365 and 121.66 rhythmic components. The salivary concentration of testosterone and the serum concentration of follitropin are the quantities with the greatest annual rhythmic variation of those studied. (C) 1998 Elsevier Science B.V.