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  • You have learnt that a characteristic feature of endocrine systems is the presence of feedback loops By what is meant if hormone A stimulates gland X to secrete hormone B the production of A could be modified

You have learnt that a characteristic feature of the endocrine system is the presence of feedback loops. By what is meant if hormone A stimulates gland 'X' to secrete hormone B, the production of  'A' could be modified when the level of B changes in our blood. An example is the relationship between the hormones LH and estrogen (E2). An old woman exhibits the following features.

High levels of LH in the blood but low levels of E2 in the blood. Another woman exhibits a high level of LH in the blood and also a high level of E2 in the blood. Where lies the defect in both these women? Provide a suitable diagram to support the answer.

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In the body, the level of LH in the blood is generally low before puberty, and it starts to increase during the reproductive phase. LH levels in the blood during the reproductive phase are dependent on the specific phase of the ovulation cycle that the woman is going through. When ovulation is about to happen, the LH level peaks, and so does the level of E2. This displays normal conditions.
                        

But in the case of older women, LH level in the bodies is higher, and it goes along with the low levels of E2. A low level of E2 is displayed at the end of the reproductive phase. It is known that menopause marks the end of the reproductive phase for the woman. After menopause, no or negligible oocytes are left in the ovary. Hence, LH is not being utilized the way it was during the reproductive phase. This explains the reason for the increased level of LH in the blood of older women.

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