Describe the relationship between different hormones regulating the menstrual cycle?

There are 4 main hormones regulating the menstrual cycle. We can split them into 2 groups: FSH (follicle stimulating hormone) and LH (luteinising hormone) made by the pituitary gland, and oestrogen and progesterone, made in the ovary, by the follicles (which contain the eggs). The hormones communicate with the organs via the blood. Starting from day 1 of the menstrual cycle (first day of period), FSH is released by the pituitary gland, which, as its name suggests, stimulates follicles to develop. One follicle will dominate and start secreting oestrogen, which leads to repair of the uterine lining. Low levels of oestrogen inhibit FSH production by negative feedback, preventing the development of more follicles. When uterine lining repair is complete, oestrogen levels in the blood reach a maximum threshold, which stimulates release of LH by positive feedback. LH leads to ovulation, where the egg is released from the follicle. But what happens to the follicle itself? LH has another role, which is to stimulate the follicle to develop into a corpus luteum. This corpus luteum continues to secrete oestrogen, and also secretes progesterone , which helps maintain the uterine lining, in preparation for implantation. These hormones inhibit FSH production by negative feedback, since we don't want another follicle to develop just yet. If the egg isn't fertilised and and so no implantation occurs, the corpus luteum degenerates and progesterone and oestrogen production stops. FSH production is no longer inhibited, which brings us back to day 1 of the menstrual cycle.

Answered by Valeriya K. Biology tutor


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