PHYSIOLOGY OF ANTERIOR HYPOPHYSIS 



257 



and collated these data with growth of the 

 gonads. For 3 weeks postnatally the total 

 glandular potency remained very low in 

 both sexes. Thereafter the cockerel pituitary 

 gained steadily in both total and unit 

 potency, reaching a plateau at about 90 

 days. The unit potency increased approxi- 

 mately five times and was accompanied by 

 an approximate parallel increase in the 

 weight of the testes of the donor birds. Pul- 

 lets over 20 days of age showed a similar 

 rise in potency plus a sharp upturn in both 

 unit and total potency coincident with the 

 burst of ovarian enlargement between the 

 115th and 125th day of life. It is precisely 

 at this point that female chickens were 

 found to become overtly responsive to mam- 

 malian gonadotrophins (Das and Nalban- 

 dov, 1955; Breneman, 1955). Among adult 

 fowl the pituitaries of nonlaying hens, as 

 tested by the mouse uterine weight method, 

 are about twice as potent as those of laying 

 hens (Riley and Fraps, 1942b). The pitui- 

 taries of mature male chickens are mark- 

 edly more potent than those of females of 

 comparable age; although the male glands 

 are heavier, the difference in potency can- 

 not be accounted for on this basis alone 

 (Riley and Fraps, 1942a; Phillips, 1943; 

 Breneman and Mason, 1951). The pituitary 

 of the male pheasant is likewise more potent 

 than that of the hen pheasant (Greeley and 

 Meyer, 1953). 



Among the most systematic studies of 

 gonadotrophic potency in relation to post- 

 natal age and sex are the early ones in rats 

 by Clark /(1935a), McQueen-Williams 

 (1935), and Stein (1935). Gonadotrophin 

 appears in assayable quantity around the 

 end of the 2nd week of life, when the gonads 

 are first becoming responsive to gonado- 

 trophic stimulation. They found a sjjike in 

 the age-potency curve for the female gland 

 at the 3rd postnatal week, which was not 

 exceeded even during sexual maturity. 



Pituitaries of adult male rats are mark- 

 edly more potent in gonadotrophic complex 

 than those of females of com})arable age. 

 Clark's data show that the relative superior 

 potency of the male gland is not attained 

 until some months after puberty. Hoogstra 

 and Paesi (1955) examined the FSH and 

 LH content of the pituitaries of intact im- 

 mature and adult male and female rats and. 



in agreement with Clark, found the total 

 FSH content of the immature female pitui- 

 tary greater than that of the adult female 

 or immature male, but not as great as that 

 of the adult male. In terms of FSH per unit 

 of glandular tissue, adult male pituitary 

 appeared to be about five times as potent 

 as the pituitary from adult females of com- 

 parable age. The LH content of the pitui- 

 taries from immature males and females 

 was low and approximately eciual; in adults, 

 the amount had increased considerably and 

 was greater in the males. 



Hollandbeck, Baker, Norton and Nalban- 

 dov (1956) estimated the potency of sow 

 pituitaries from birth through 1330 days of 

 age, using the chick testis assay. The results 

 were expressed in terms of the weight of the 

 anterior lobe and correlated with age and 

 body weight. The unit potency decreased 

 linearly with age, whereas total potency 

 showed a linear increase, because, of course, 

 the weight of the pituitary increased with 

 age. The amount of hormone available per 

 unit of body weight was very high at birth 

 and declined through the prepubertal period 

 to a low level which remained nearly con- 

 stant from puberty onward. This steady 

 drop in available hormone per unit of body 

 weight through the jjrepubertal period is not 

 in accord with the general assumption that 

 an increase in titer of circulating gonado- 

 trophin precedes puberty. Such data do not 

 rule out a likely increase in secretion of 

 gonadotrophin nor, as the authors have sug- 

 gested, the possibility that an imbalance 

 may have occurred in the ratio at which the 

 gonadotrophic factors, FSH and LH, were 

 secreted. The high potency during infancy 

 was thought to be due to the presence of 

 mainly FSH. The initiation of cyclic ovar- 

 ian activity at puberty was thought to 

 signify augmented secretion of LH, yielding 

 a more functionally balanced FSH-LH 

 ratio. Similarly, from evidence based on the 

 urinary excretion of FSH and LH in the 

 human female, Brown (1958) showed that 

 the prepubertal period may be characterized 

 by a rising level of LH. 



Among the primates informative data re- 

 lating to the ratio and content of FSH and 

 LH in the hypophysis in relation to sex and 

 age have been obtained only for man. Bahn 

 and associates (1953a-d) studied the FSH 



