35.- 36. Essay – The following is a paragraph from a treatise on osteoporosis: \

Question

35.- 36. Essay – The following is a paragraph from a treatise on osteoporosis: "In summary, the multifaceted activities of estrogen are fully reflected in bone. Of the many surprises encountered investigating estrogen action in bone is the relationship among estrogen, the immune system, and the skeleton (Figure 3 not show here). Clearly, if this relationship is equally relevant in humans as in rodents, postmenopausal osteoporosis should be regarded as the product of an inflammatory disease bearing many characteristics of an organ-limited autoimmune disorder, triggered by estrogen deficiency, and brought about by chronic mild decreases in T cell tolerance. Why such a pathway should have emerged is intriguing. One explanation is suggested by the need to stimulate bone resorption in the immediate postpartum period in order to meet the markedly increased maternal demand for calcium brought about by milk production. The signal for this event is the drop in estrogen levels early postpartum. Henry Kronenberg (Harvard University, Boston, Massachusetts, USA) has suggested that postmenopausal bone loss should be regarded as an unintended recapitulation of this phenomenon (personal communication). Another response to delivery is the restoration of normal immune reactivity and the loss of tolerance to the fetus. It is tempting to speculate that cessation of ovarian function induces bone loss through an adaptive immune response because natural selection has centralized these 2 key adaptations to postpartum within the immune system. “

What aspect of the aging body does the author fell is responsible for post-menopausal osteoporosis and what makes him suspect this?

Explanation / Answer

The ageing or post menopausal body experiences a sharp decline in circulating estrogen levels. Such low levels of estrogen lead to a inflammatory condition that resembles organ specific autoimmunity, due to a low estrogen driven T cell deficiency.

The author has said that bone loss in the ageing body can be regarded as an event reminiscent of the increased bone resoprtion rates in the post partum female body, due to rapid loss in calcium because of lactation. Both events are low estrogen level driven events.

The age induced cessation of ovarian function, which induces bone loss through an adaptive immune response such as reduction in T cell numbers, among other events, can be thought to be evolutionarily reminiscent of the loss of fetal tolerance and restoration of the maternal immune system (post delivery).

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