HORMONES 



297 



Progesterone 



Testosterone 



Androsterone 



Androgenic hormones 



Estradiol, progesterone, and testosterone appear to be the true, primary 

 hormones, since they are considerably more active, weight for weight, 

 than the others. The chemical structures of all the steroid hormones 

 appear to be remarkably similar for substances having such widely 

 different biological properties (compare p. 290). The structures of the 

 estrogens and androgens can be modified considerably, however, without 

 marked loss of potency. For example, stilbestrol and doisynolic acid 

 are about as effective as estrone, and the former, in fact, is even more 

 active than estrone when given orally (Table 11-1). On the other hand, 



H,^ H 



II I H 



C H U 

 H ^ Hs 



Stilbestrol 



Doisynolic acid 



almost any change in the progesterone molecule produces an inactive 

 product. 



Thyroid hormone 



The thyroid gland is a small mass of specialized tissue — about 30 g. 

 in the human adult — located in the neck near the larynx. It produces 

 a hormone which greatly stimulates metabolic activity, particularly the 

 oxidative, energy-yielding processes. Iodine has long been recognized 

 as related to thyroid function (for example, in goiter), but it was not 

 until 1919 that the isolation of an active substance, thyroxine, from thyroid 

 tissue was reported by Kendall. A related substance, diiodotyrosine 

 or iodogorgoic acid, has also been isolated from thyroid, and, in fact, 

 accounts for about two-thirds of the total iodine content of the gland. 



