Concept encyclopediaHormones
Melatonin
Or pineal hormone: the pineal gland in the brain responds to an absence of light (or to any stress which increases the adrenalin systems) by secreting a hormone called melatonin, which lightens the skin, makes the brain sluggish, turns off thyroid and progesterone production, and suppresses immunity and fertility.
Melatonin is a hormone secreted by the pineal gland in the brain in response to an absence of light or stress, which lightens the skin, makes the brain sluggish, turns off thyroid and progesterone production, and suppresses immunity and fertility .
The absence of melanin in the skin makes individuals more sensitive to light, and bright light suppresses melatonin production, causing the skin to turn dark brown or black, which protects it from bright sunlight . In the retina, melatonin increases the sensitivity of cells to dim light and helps produce dark adaptation of the eyes .
Melatonin also has a suppressive effect on the thyroid gland, and its production is inversely related to thyroid activity, with thyroid levels increasing with age and melatonin levels decreasing . In pigs, melatonin has been shown to suppress progesterone production, and in humans, it has been found to lower the threshold of light sensitivity of the retina .
Melatonin has a protective effect on the brain by turning off the vicious cycle of nitric oxide and acetylcholine activation, which can keep the brain awake in a fatigued state . However, in high doses, melatonin can increase the susceptibility of photoreceptors to light-induced damage . Additionally, melatonin has been found to constrict small diameter cerebral arterioles in rats, which may have implications for its effects on blood pressure and circulation .
People also ask
- What does melatonin do in the body?Melatonin, secreted by the pineal gland, can lighten skin, make the brain sluggish, suppress thyroid and progesterone, and inhibit immunity and fertility. It also increases retinal sensitivity to dim light.
- How does light affect melatonin?The corpus describes that bright light suppresses melatonin production, which causes skin to darken for protection. Melatonin itself increases the retina's sensitivity to dim light.
- Does melatonin interact with other hormones?Yes, melatonin has a suppressive effect on the thyroid gland, with an inverse relationship between their activity. It has also been shown to suppress progesterone production.