Which is the major hormone secreted by the corpus luteum in a lady of reproductive age?
**Core Concept:** The corpus luteum (CL) is a temporary structure that forms after the fertilization of an egg (ovulation) in a woman of reproductive age. It is responsible for producing hormones that regulate the menstrual cycle and prepare the uterus for pregnancy. The primary hormone secreted by the CL is progesterone (P4).
**Why the Correct Answer is Right:** Progesterone (P4) is a steroid hormone that plays a crucial role in maintaining the corpus luteum and ensuring a healthy endometrial environment for implantation. It supports the endometrial lining, prevents uterine contractions, and suppresses the production of luteolytic substances that would otherwise cause the corpus luteum to degenerate.
**Why Each Wrong Option is Incorrect:**
A. Human Chorionic Gonadotropin (hCG): While hCG is also produced by the corpus luteum, it is not the major hormone secreted. Its role is to prevent luteolysis (the process of corpus luteum degradation) and is primarily produced during pregnancy, not in a non-pregnant state.
B. Estrogen (E2): Estrogen (E2) is a hormone produced by the follicle during the menstrual cycle. In contrast to progesterone, estrogen does not play a significant role in maintaining the corpus luteum.
C. Thyroid Stimulating Hormone (TSH): TSH is the hormone secreted by the pituitary gland that regulates thyroid hormone production. It is not produced by the corpus luteum.
D. Prolactin (PRL): Prolactin is a hormone produced by the anterior pituitary gland, regulating lactation and milk production. It is not the major hormone secreted by the corpus luteum.
**Clinical Pearl:** Adequate progesterone production is essential for maintaining a healthy uterine environment and preventing anovulation (the absence of ovulation) in subsequent cycles. The correct answer (progesterone) ensures the proper development of the endometrium, preventing it from shedding prematurely and preparing the uterus for potential implantation. Inadequate progesterone production can lead to menstruation and eventually result in infertility.