Did you mean: epiphysis, distal part of the long bones or pituitary, an "other endocrine gland
The epiphysis is a small endocrine gland located in the center of the skull, where it makes up a large part of the epithalamus. Also known as the pineal gland (due to the shape that is broadly similar to that of a pine cone), the epiphysis is responsible for the synthesis and secretion of a hormone, called melatonin.
From the anatomical point of life, the epiphysis is covered by a connective covering capsule, made up of the same connective tissue as the pia mater. Inside the gland we recognize a parenchyma consisting of two main cell types: a dense weave of interstitial cells that act as a support to endocrine cells called pinealocytes (or main cells), which synthesize melatonin.
Despite the small size (diameter of about 8mm) and the negligible weight (0.1 g), the epiphysis is far from being a superfluous structure, as it was described until a few decades ago; in fact, melatonin is a key hormone in regulating the sleep-wake cycle.
The pineal gland or epiphysis also has an inhibitory effect on the pituitary-gonadal axis; not surprisingly, if its removal or surgical ablation is performed in the pre-pubertal period, there is an early onset of puberty, while when it is performed in age adult is accompanied, especially in males, by hypergonadism.This effect is more marked in animals that have a reproductive season in the period in which the day is longer (therefore, as we will see, the secretion of melatonin is minimal).
Melatonin also appears to be able to influence the levels of leptin, GH and probably those of many other hormones, since in addition to regulating circadian (daily) rhythms, it also helps to modulate seasonal rhythms. As if that weren't enough, the pineal gland is richly vascularized, with a relative blood supply second only to that of the kidney.
Melatonin also exerts an important stimulatory effect on the immune system.
This hormone should not be confused with melanin, a skin pigment that gives dark tones to the skin, hair and eyes; in reality, even if only in amphibians, melatonin has opposite effects on the skin compared to melanin.
In mammals, including humans, melatonin is produced by pinealocytes (epiphysis cells responsible for this synthesis) starting from the amino acid tryptophan, which is converted into serotonin, then into acetylserotonin and finally into melatonin. The activity of this enzyme increases at night and decreases during the day; consequently, the secretion of melatonin is stimulated by the dark and inhibited by light. Recent studies indicate that the production of melatonin by the epiphysis also changes in relation to changes in the earth's magnetic field.
The therapeutic use of melatonin is wide and still evolving, given its hypnotic (induces sleep), antidepressant (improves mood disorders), neuroprotective and antioxidant properties (both melatonin and its metabolites are able to neutralize reactive oxygen and nitrogen species).
The epiphysis was once considered useless, due to the numerous calcification points found inside it. Today we know that the process of calcification of the gland begins during puberty and continues in adulthood and old age, gradually undermining it. the effectiveness.
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