Question

mesturation is triggered by an abrupt decline in the amount of

Answer 1

Progesterone,,, is your answer

Answer 2

Hi!!! here is your answer ....

The corpus luteum secretes large amounts of progesterone which is essential for maintenance of the endometrium (wall of the uterus) . Such an endometrium is necessary for implantation of the fertilized ovum. In the absence of fertilization, the corpus luteum degenerates resulting in decline in the progesterone level. This causes disintegration of the endometrium leading to menstruation, making a new cycle. 

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