Significance of the pineal gland in female neuroendocrine homeostasis

Numerous experimental studies have proved the suppressive effect of epiphysis on sex gland secretion, which is explained by the primary influence of the pineal gland on gonadotropin formation. Intraventricular administration of the epiphysis hormone melatonin leads to the accumulation of neurosecretin in the hypothalamic nuclei and blocks its release into the posterior pituitary lobe. The central effect of melatonin is manifested in the suppression of secretion of luteotropic hormone (LH) and follicle stimulating hormone (FSH) by the pituitary gland. Studies conducted by E.I. Chazov and V.A. Isachenkov testify to a high degree of dependence of luteotropic hormone formation on the pineal gland. Additionally, the authors demonstrated that the involvement of the epiphysis in the regulation of luteotropic hormone synthesis is not lost after puberty, but persists for a long period of the reproductive stage. The amplitude of the effect of the epiphysis on the level of luteotropic hormone formation depends on its functional state, determined by the degree of ambient light. It was found that luteotropic hormone synthesis peaks at certain times of the day, depending on the season of the year: at 15 h in spring and at 3 h in other seasons.