Starvation induced anoestrus: effect of chronic food restriction on body weight, its influence on oestrous cycle and gonadotrophin secretion in rats

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Abstract
To test the effect of chronic starvation on gonadotropin secretion and estrous cycles, rats were fed 50% of their normal chow consumption for 16 days. This caused an increasing rate of anestrus which became significant during the 3rd expected cycle (6 of 10 rats, P < 0.02) and increased 8 of 10 rats (P < 0.0001) between day 12 and 16. The accompanying wt loss was around 13 and 17%, respectively. Pituitary wt in intact rats killed on diestrus became significantly different after 8 days of chow reduction (12.8 .+-. 0.2 vs. 11.3 .+-. 0.4 mg, P < 0.02) with further reductions in groups killed after 12 and 16 days. At this time diestrous serum FSH levels were significantly increased in starved rats (112 .+-. 16 vs. 161 .+-. 13 ng/ml, P < 0.01), while serum LH [luteinizing hormone] levels decreased significantly after 12 days (25.0 .+-. 3.4 vs. 13.1 .+-. 8.8 ng/ml, P < 0.001). Starvation decreased the LH response to LHRH administration compared to proestrous controls (1934 .+-. 672 vs. 289 .+-. 39 ng/ml, P < 0.05); the FSH response was not impaired (457 .+-. 91 vs. 336 .+-. 54 ng/ml, P > 0.05). In contrast to this pituitary content of LH was similar in both groups, while FSH content was significantly higher in starved animals (13.6 .+-. 1.7 vs. 19.8 .+-. 1.2 .mu.g, P < 0.01). Chronic starvation immediately after ovariectomy did not affect the post-castrational rise of gonadotropins. However, LHRH administration caused higher serum FSH levels in starved rats (1540 .+-. 91 vs. 1833 .+-. 90 ng/ml, P < 0.05); LH values did not differ (908 .+-. 192 vs. 721 .+-. 153 ng/ml, P < 0.05). Gonadotropin content per pituitary in castrated rats after 16 days of starvation was unchanged.