Inhibition of HCG induced testosterone increase by melatonin-free pineal extract in the rat

The effect of a pineal treatment on rat testosterone under conditions of exogenous HCG stimulation was followed-up. Administration of 2 ml/day/animal of a melatonin-free pineal extract for 3 days lowered by 23% (p less than 0.01) the serum level and by 32% (p less than 0.02) the testis content in testosterone, both values being increased by concomitant administration of 50 UI HCG per animal. In other words, the melatonin-free pineal extract inhibited partially the testis response to HCG. The antiandrogenic action of the pineal extract is discussed.