A example of negative feedback

a. elevated free t4 resulting in elevated trh
b. elevated free T4 resulting in elevated tsh
c low free T4 resulting in elevated tsh
d. low free t4 resulting in low tsh

i think its B. not sure.

To determine the correct answer, we need to understand the concept of negative feedback in the context of thyroid hormone regulation.

Negative feedback is a mechanism by which the body maintains homeostasis by counteracting any deviations from the normal range. In the case of thyroid hormone regulation, negative feedback involves the hypothalamus, the pituitary gland, and the thyroid gland.

The hypothalamus produces thyrotropin-releasing hormone (TRH), which stimulates the pituitary gland to release thyroid-stimulating hormone (TSH). TSH then acts on the thyroid gland to stimulate the production and release of thyroxine (T4) and triiodothyronine (T3), which are the main thyroid hormones.

Now, let's evaluate each option:

a. Elevated free T4 resulting in elevated TRH: This scenario would not be an example of negative feedback, as elevated free T4 levels would indicate an already high thyroid hormone level, which would not stimulate the hypothalamus to increase TRH production.

b. Elevated free T4 resulting in elevated TSH: This scenario fits the concept of negative feedback. When free T4 levels are high, the pituitary gland senses this and reduces the production and release of TSH, thereby inhibiting further thyroid hormone production.

c. Low free T4 resulting in elevated TSH: This scenario would not be an example of negative feedback, as low free T4 levels would indicate a low thyroid hormone level, which would stimulate the pituitary gland to increase TSH production, rather than inhibiting it.

d. Low free T4 resulting in low TSH: This scenario would not be an example of negative feedback either. Low free T4 levels would typically stimulate the pituitary gland to increase TSH production, as the body tries to compensate for the low thyroid hormone levels.

Therefore, the correct answer is option b: elevated free T4 resulting in elevated TSH, which represents negative feedback in thyroid hormone regulation.