THE GONADOTROPIC HORMONES 



ing gonadotropic hormones such as prolan or pregnant- mare 

 serum. ^-i The observations of Tyndale and Levin (1937) sup- 

 port Leonard's conclusions. These authors found that the 

 ovarian response to foUicle-stimulating hormone (extract of 

 "menopause urine") may be much greater in hypophysec- 

 tomized than in normal immature rats. Inasmuch as the in- 

 jection of thyroxine reduced the ovarian response of similarly 

 treated hypophysectomized rats, they concluded that poor 

 function on the part of the thyroid may account for the dif- 

 ference found. Obviously this suggestion does not exhaust the 

 list of possible explanations. Thyroid hormone probably pro- 

 duces an inhibitory effect by its action on the ovary (see also 

 Fischer and Engel, 1936). On the other hand, the results of 

 Morrin and Loeb (1935) indicated that the response of the 

 guinea pig's ovary to implants of the pars glandularis (guinea 

 pig, ox, rabbit, and rat) was the same whether or not the thy- 

 roid had been removed previously. 



Halpern and Hendryson (1935) reported that dinitro- 

 phenol, a general stimulant of metabolism, does not signifi- 

 cantly affect the oestrous cycles of rats and that changes in 

 the oestrous cycles caused by thyroid extract therefore can- 

 not be attributed to the stimulating effect of the extract on 

 metaboHsm. 



2. The adrenal glands. — The hormonal variables requiring 

 attention in a consideration of the interrelationship of the 

 pituitary (gonadotropic function) and adrenal glands are pi- 

 tuitary gonadotropic hormones, adrenal cortical stimulating 

 hormone, and the internal secretions of both the gonads and 

 the adrenal cortex." Moreover, the internal secretions of the 

 "end-organs," the gonads and the adrenal cortex, are prob- 

 ably so similar in structure that, under suitable conditions, 



s-t Loeb, Saxton, and Hayward (1936) believed that thyrotropic hormone usually 

 is associated with luteinizing hormone and "atresin" in the pituitary. The concen- 

 tration of follicle-stimulating hormone tends to be low if that of the other three 

 substances is high. 



55 Epinephrine, the important medullary secretion, appears to require no con- 

 sideration. 



[95] 



