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

To test the effect of chronic starvation on gonadotrophin secretion and oestrous cycles, rats were fed 50% of their normal chow consumption for 16 days. This caused an increasing rate of anoestrus which became significant during the third expected cycle (6 of 10 rats, P less than 0.02) and increased to 8 of 10 rats (P less than 0.0001) between day 12 and 16. The accompanying weight loss was around 13 and 17%, respectively. Pituitary weights in intact rats killed on dioestrus became significantly different after 8 days of chow reduction (12.8 +/- 0.2 vs 11.3 +/- 0.4 mg, P less than 0.02) with further reductions in groups killed after 12 and 16 days. At this time dioestrous serum FSH levels were significantly increased in starved rats (112 +/- 16 vs 161 +/- 13 ng/ml, P less than 0.01), while serum LH levels decreased significantly after 12 days (25.0 +/- 3.4 vs 13.1 +/- 8.8 ng/ml, P less than 0.001). Starvation decreased the LH response to LRH administration compared to pro-oestrous controls (1934 +/- 672 vs 289 +/- 39 ng/ml, P less than 0.05), whereas the FSH response was not impaired (457 +/- 91 vs 336 +/- 54 ng/ml, P greater than 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 micrograms, P less than 0.01). Chronic starvation immediately after ovariectomy did not affect the post-castrational rise of gonadotrophins. However, LRH administration caused higher serum FSH levels in starved rats (1540 +/- 91 vs 1833 +/- 90 ng/ml, P less than 0.05), whereas LH values did not differ (908 +/- 192 vs 721 +/- 153 ng/ml, P greater than 0.05). Gonadotrophin content per pituitary in castrated rats after 16 days of starvation was unchanged.