Question

Melatonin supress hypothalamus, causes suppression of the anterior pituitary gonadotropins leading to suppression of mensuration and gonadel activity.

DOES THAT MEAN HYPOTHALAMUS IS UNDER CONTROL OF MELATONIN ??

Explain please....!

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Answer 1

Melatonin was first isolated from the bovine pineal gland in 1958.1 In humans, it is the main hormone synthesized and secreted by the pineal gland. It is produced from a pathway that includes both tryptophan and serotonin. Melatonin displays high lipid and water solubility, which allows it to diffuse easily through most cell membranes, including the blood-brain barrier. Its half-life is about 30 minutes, and it is cleared mostly through the liver and subsequently excreted in the urine as urinary 6-sulfatoxymelatonin.

In humans and most diurnal mammals, melatonin is secreted at night with a robust circadian rhythm and maximum plasma levels that occur around 3 to 4 AM. The daily rise of melatonin secretion correlates with a subsequent increase in sleep propensity about 2 hours before the person’s regular bedtime. The time before this secretion is the least likely for sleep to occur, and when it starts, the propensity for sleep increases greatly as the “sleep gate” opens. The rhythmic release of melatonin is regulated by the central circadian rhythm generator—the suprachiasmatic nucleus (SCN) of the anterior hypothalamus.

Answer 2

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★ No, hypothalamus is not under control of melatonin.

★ The effect of melatonin on reproductive systems can be summarised by saying that it is anti-gonadotropic.

★ In other words, melatonin inhibits the secretion of the gonadotropic hormones- luteinizing hormone and follicle stimulating hormone from the anterior pituitary.

★ Much of this inhibitory effect seems due to inhibition of gonadotropin-releasing hormone from the hypothalamus, which is necessary for secretion of the anterior pituitary hormones.

★ We cannot say that hypothalamus is under the control of melatonin. This hormone exerts inhibitory action on the hypothalamus and regulates gonadotropic hormones.

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