Estrus-Inhibiting Effects of Inanition

Abstract

The effects of complete and partial starvation upon the estrous cycle of adult female rats were studied. Smears from the vaginal mucosa were taken for at least 2 weeks before any experimental procedures were instituted. Seven groups of 5 rats each were used. One group was kept as control; 2 groups received no food or water, and another only water at the onset of starvation; the fifth group was starved intermittently so that the loss of weight was more gradual. The remaining 2 groups were starved completely without water until they died. Each animal was weighed daily. The water and food consumption of the groups fed was recorded daily. It was found that the animals in all the starved groups eventually showed complete inhibition of the estrous cycle, and that the inhibition was roughly related to the loss in body weight, as shown in the table. When the inhibition of the estrous cycle was complete, all but 2 groups were fed again, with resulting return to the normal cyclical changes in the vaginal mucosa.

Experiments to Determine the Factors Involved. In analyzing the estrus-inhibiting effects of starvation, one must distinguish between an inability of the vaginal mucosa to respond to estrogenic hormone; and the possibility that the ovaries have ceased to produce the hormone during the period of inanition. If the latter be true, one must further distinguish between a primary failure of the ovary, and a failure of the pituitary gland to produce the gonadotropic hormone. It is conceivable that any or all of these factors may be involved.

1. The effect of estradiol monobenzoate upon the inanition anestrus. Two groups of 10 rats were starved completely for 6 days. On the day starvation was begun 4 of the 10 animals were in estrus; 3 were just entering the diestrous phase; 2 were in diestrus: and 1 was in proestrus.