[Seasonal variations of testicular and pituitary function in men].

In 21 young, healthy men typical parameters of pituitary and testicular function were recorded over a period of one year in intervals of two months. The mean sperm count in semen had a minimum in december, a maximum in june. Serum-FSH showed low levels in june, october and december, a peak in august. Levels of FSH following stimulation by LH-RH varied in the same manner, but the response to LH-RH was lower in april. A peak of serum-LH appeared in april, other values being rather constant. The response to LH-RH showed parallel variations. Testosterone levels exhibited a significant peak in june. The mean increase of testosterone following hCG depended on basal levels, but showed a distinct peak in december.