Question

The hormone ‘melatonin’ is secreted by the gland
(a) Thyroid
(b) Adrenal
(c) Pineal
(d) Pituitary

Answer 1

Hint: Melatonin is secreted by a small endocrine gland in the brain of most vertebrates. It is reddish-brown in color and surrounded by a capsule. This gland tends to be wasted after puberty.

Complete answer:
The hormone ‘melatonin’ is secreted by the Pineal gland that regulates the sleep- wake cycle. The pineal gland is a small body attached to the roof of the third ventricle and is connected to it by a short stalk containing nerves, many of which terminate in the hypothalamus. It is about 10mm long reddish- brown in color and surrounded by a capsule. This gland tends to be wasted after puberty (time in life when a boy or girl becomes sexually mature) and may become calcified in later life.
Melatonin is the main hormone secreted by the pineal gland. Secretion is controlled by daylight and levels fluctuate during each 24- hour period, being highest at night and lowest around midday. Secretion is also influenced by the number of daylight hours, i.e. seasonal variations.
Although its function is not fully understood, melatonin is believed to be associated with:
- Coordination of the circadian and diurnal rhythms of several tissues, happen by regulating the hypothalamus.
- Inhibition of growth and development of the sex organs before puberty, possibly preventing synthesis or release of gonadotropins (LH and FSH hormones).
So, the correct answer is ‘Pineal’.

Note: Melatonin was first discovered in connection to the mechanism by which some amphibians and reptiles change the color of their skin. It is also used as a medicine to treat insomnia.