Testosterone

The correct answer is Option (4) - Testosterone

The menstrual cycle, a recurring series of physiological changes in female primates, is regulated by hormones such as FSH, LH, estrogen, and progesterone. FSH initiates the development of follicles, leading to estrogen secretion. Elevated estrogen levels prompt the thickening of the uterine endometrium. LH, released by the pituitary gland, induces ovulation. Following the LH surge, progesterone rises, converting follicles into corpus luteum. Corpus luteum secretes progesterone, crucial for maintaining the uterus lining for potential implantation. The concurrent elevation of progesterone and estrogen leads to a decline in FSH and LH. In the absence of pregnancy, diminishing progesterone and estrogen levels result in endometrial shedding, marking the onset of menstrual flow. Subsequently, FSH and LH levels rise to initiate a new cycle after menstruation begins.