Human Reproduction

Phases of the menstrual cycle and their hormonal control are central to NCERT Class 12, Chapter 3 (Human Reproduction). After ovulation, the ruptured follicle transforms into the corpus luteum, which secretes large amounts of progesterone. During the resulting secretory or luteal phase, progesterone maintains the thickened, glandular endometrium and prepares it to receive an embryo. Oestrogen from the growing follicle is incorrect because it predominates during the earlier follicular and proliferative phase, promoting endometrial growth rather than its secretory maintenance. Inhibin from granulosa cells mainly suppresses follicle-stimulating hormone and does not sustain the endometrium. Luteinizing hormone from the pituitary triggers ovulation and supports the corpus luteum, but it is the progesterone produced under its influence, not LH directly, that maintains the lining. A timing check confirms the answer: the secretory phase follows ovulation, exactly when corpus luteum progesterone is at its peak, making it the principal maintaining hormone.