Posted by Ted (152.163.197.177) on January 29, 2000 at 20:31:29:
In Reply to: Good answer, but to what relevance? posted by Q on January 29, 2000 at 19:47:30:
The hypothalamus bone is connected to the pituitary-gland bone. The Pituitary-gland bone is connected to the thyroid gland bone. TRH from the hypo stimulates the TSH, which comes from the PG. It stimulates the making of T4 and T3 when it hits the thyroid. Ahhhh, just read the quote below. Frankly, I am not much of a goiter expert. But there are certain correlations that I see in the disease that implicates the hypo and its functioning properly with getting goiter. Don't let the fact that they know what causes goiter but not CHs throw you off.
"TSH is a peptide hormone secreted by the pituitary gland. It stimulates the synthesis and secretion of T4 and T3 (triiodothyronine) from the thyroid gland. TSH is, itself, stimulated by TRH, which is released by the hypothalamus. T3 and T4 feedback inhibit the release of both TSH and TRH in normal people. Most of the thyroid hormone secreted by the thyroid gland is in the form of T4, but T3 is probably the active hormone; i.e., T4 is converted to T3 by target tissues.
T4 is the major hormone controlling the basal metabolic rate. The exact mechanisms are not completely known, but it is known that T4 increases the concentrations of numerous enzymes involved in the production of energy in all nucleated cells of the body. Most of the T4 in the blood is bound to proteins; this acts as a reservoir of available thyroxine because only free T4 is active on cells. T4 appears to be converted to T3 within cells, before it enters the nucleus and interacts direction with DNA, eventually resulting in the production of various proteins by the cell."