Circle the answer (high, low or normal) for each of the questions below. a) If a

Question

Circle the answer (high, low or normal) for each of the questions below.

a) If a person has primary hypocortisolism, would their levels of ACTH be high, low or normal?

b) If a person has secondary hypothyroidism due to a problem with the pituitary gland, would their levels of TRH be high, low or normal?

c) If a person has secondary hypercortisolism due to a problem with their hypothalamus, would their levels of CRH be high, low or normal?

d) If a person has primary hypercortisolism, would their levels of CRH be high, low or normal?

e) If a person has Grave's Disease, would their levels of TRH be high, low or normal?

f) If a person has Addison's Disease, would their levels of ACTH be high, low or normal?

Explanation / Answer

a) The hypothalamus secretes corticotropin releasing hormone (CRH) which stimulates anterior pituitary gland to release adrenocorticotropic hormone (ACTH). ACTH acts on adrenal cortex to release aldosterone and cortisone. When the levels of aldosterone and cortisone raises in plasma, they exert negative feedback mechanism on hypothalamus and anterior pituitary to reduce the levels of CRH and ACTH. Therefore, in primary hypercortisolism, the levels of ACTH are low.

b) TRH is released by hypothalamus. It stimulates TSH secretion from anterior pituitary. TSH stimulates thyroid gland to secrete thyroid hormones. In secondary hypothyroidism, TSH levels will be low. This decreases thyroid hormone levels. So, TRH secretion by hypothalamus will be increased.

c) CRH is released from hypothalamus. So, if there is a problem in hypothalamus, CRH levels will be low.

d) In primary hypercortisolism, CRH levels will be low due to negative feedback mechanism by cortisol on hypothalamus.

e) In Grave's disease, TRH levels are low, due to negative feedback mechanism by thyroid hormones on hypothalamus.

f) In Addison's disease, adrenal cortex does not produce enough hormones. So, the levels of ACTH will be high.

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