Progesterone's Role in Pregnancy & Lactation — NEET Biology

Correct answer: A — A

The core concept distinguishes the direct functions of progesterone from those of estrogen or other related processes. Progesterone's functions include: - Supports pregnancy (including maintenance of uterine endometrium and inhibition of uterine contractions). - Acts on mammary glands to stimulate alveoli formation and milk secretion. Let's evaluate the options: A. Regulation of female sexual behaviour: Estrogen regulates female sexual behaviour. While progesterone has roles related to reproduction, directly regulating female sexual behavior is more characteristic of estrogen. Therefore, this is LEAST likely a direct function of progesterone. B. Maintenance of uterine endometrium for implantation: Progesterone supports pregnancy, which inherently involves maintaining the uterine endometrium for implantation and supporting the early stages. This is a direct function. C. Stimulation of overall mammary gland development: Estrogen is largely responsible for overall mammary gland development. Progesterone stimulates the *formation of alveoli* and milk secretion, which is a specific aspect of mammary gland function, not the overall development from scratch. However, NCERT states "mammary gland development" for estrogen. Progesterone acts *on* mammary glands for alveoli formation. So, 'overall mammary gland development' is more accurately estrogen's role. So, this is also less likely a *direct* function of progesterone, compared to its specific role in alveoli formation and milk secretion. D. Inhibition of uterine contractions during pregnancy: This is a crucial function of progesterone to maintain pregnancy. This is a direct function. E. Stimulation of milk secretion after alveoli formation: This is explicitly stated as a function of progesterone. This is a direct function. Comparing A and C, 'Regulation of female sexual behaviour' is explicitly stated as an estrogen function, while progesterone is linked to specific mammary gland actions (alveoli formation and milk secretion), distinct from overall development. Thus, 'Regulation of female sexual behaviour' (A) is the *least likely* direct function of progesterone.