Question

Which of the following is proteinaceous in chemical nature?
A. Oxytocin
B. Estrogen
C. Progesterone
D. Testosterone

Answer 1

Hint: It is a proteinaceous structure consisting of amino acids and a peptide hormone which is produced in the hypothalamus and released by the pituitary is proteinaceous in nature. It is involved in childbirth and milk production.

Complete answer: Oxytocin is a peptide hormone which is secreted by the pituitary gland. It is a G-protein coupled receptor hormone which is activated by magnesium ions and cholesterol. It is one of the rhodopsin-type G-protein coupled receptors which is formed in the hypothalamus. It is a hormone as well as an important neurotransmitter. It plays a vital role in childbirth, milk production, social bonding, reproduction, etc. Oxytocin is encoded by the gene name ‘OXT’ gene and is derived from enzymatic splitting of peptide precursors. The precursor undergoes progressive hydrolysis and then results in active oxytocin formation. The PAM or peptidyl glycine alpha-amidating monooxygenase enzyme catalyses the formation of oxytocin from its precursor. The activity of this enzyme is dependent on vitamin C. It is made of nine amino acid sequences. Oxytocin levels are regulated by estrogen levels. Estrogen increases oxytocin secretion. Oxytocin has both neural and peripheral actions. In peripheral functions, the uterine muscle contractions and milk ejection reflex are the most important functions of oxytocin. In neural functions, oxytocin is known to regulate stress, anxiety, and social bonding behaviour. Human sexual response is also regulated by oxytocin. Henry Dale in 1906 discovered oxytocin.
Thus, the correct answer is option A.

Note: Oxytocin is often used as a medication that facilitates childbirth. Oxytocin has some similarity to vasopressin and thus it can reduce urine excretion slightly. Therefore, it is also regarded as an antidiuretic. Thus, oxytocin is an important hormone as well as a neurotransmitter.