Question

Mammalian biorhythms may be due to differential secretion of
(a) FSH
(b) MSH
(c) Melatonin
(d) Sex corticoids

Answer 1

Hint: Biorhythms or biological rhythms control sleep and wake cycles and perform other functions like behavior and endocrine rhythms. The functions are regulated by the circadian clock.

Complete solution:
Follicle-stimulating hormone (FSH) is a gonadotropin secreted by the pars distalis region of the pituitary gland which is commonly called the anterior pituitary. In males, FSH stimulates spermatogenesis and normal functioning of seminiferous tubules. In females, it stimulates the oogenesis and development of Graafian follicles in the ovary.
Melanocyte stimulating hormone (MSH) is secreted by the pars intermedia region of the pituitary gland. MSH stimulates the melanocytes to synthesize melanin in mammals. It darkens the complexion of the skin by distributing melanin evenly under the skin.
The pineal gland secretes a hormone called Melatonin. This hormone plays a very important role in the regulation of a 24-hour (diurnal) rhythm of our body. It helps in regulating the normal rhythms of the sleep-wake cycle.
Sex corticoids are the sex hormones that are separate in males and females.
Testosterone is responsible for regulating the development, maturation, and functions of male accessory sex organs. The stimulation of muscle growth, growth of facial and axillary hair, aggressiveness, low pitch of voice, etc in males are some functions performed by testosterone.
In females, Estrogen and Progesterone are the sex hormones produced by ovaries.
Estrogen regulates female sexual behavior.
Progesterone supports pregnancy and stimulates milk secretion.

Additional information:
Circadian rhythm is a natural, internal process that regulates the sleep-wake cycle and gets repeated on each rotation of earth every 24 hours. These rhythms are driven by a circadian clock.

So, the correct answer is ‘Melatonin’.

Note:
Melatonin should not be confused with melanin. Melatonin is a hormone secreted by the pineal gland whereas melanin is a pigment found in the skin that determines the skin color.