Endocrine Effects of Pineal Gland and of Melatonin

Abstract

Pinealectomy when performed in male rats results in a significant increase in weight of the testes, the prostates and the seminal vesicles. This suggests that the pineal gland usually inhibits the secretion of LH [luteinizing hormone] and FSH [follicle-stimulating hormone]. Melatonin administered to male rats diminishes the weights of prostates and of seminal vesicles, but does not change testicular weight, indicating that exogenous melatonin suppresses the secretion of LH, but does not interfere with FSH release. In prepuberal female rats melatonin retards puberty and decreases pituitary weight as well as the weights of the ovaries and the uteri, confirming that melatonin reduces LH secretion. The pineal gland exerts an anti-FSH effect through compounds different from melatonin.