DOCOSAHEXAENOIC ACID INCREASES THYROID-STIMULATING HORMONE CONCENTRATION IN MALE AND ADRENAL CORTICOTROPIC HORMONE CONCENTRATION IN FEMALE WEANLING RATS

Circulating levels of thyroid-stimulating hormone (TSH), growth hormon e (GH), adrenal corticotrophic hormone (ACTH) and prolactin (PRL) were assessed in suckling rats in the postweaning period after rats were f ed diets that reflect the fat composition of a current infant formula with or without the addition of 1.2 g/100 g fatty acid arachidonic aci d [20:4(n-6)] and 0.7 g/100 g fatty acid docosahexaenoic acid [22:6(n- 3)] or both 20:4(n-6) and 22:6(n-3), At 2 wk of age, no effect of diet on circulating levels of TSH, ACTH, GH or PRL was apparent. By 6 wk o f age (3 wk postweaning), male rats consuming the diet containing 22:6 (n-3) had significantly elevated levels of TSH, and females had signif icantly higher ACTH concentrations than males. No effect of diet was o bserved on circulating GH or PRL levels, Male pups had higher levels o f TSH than females (P < 0.0001), whereas female pups from the 22:6(n-3 ) diet treatment exhibited much higher levels of ACTH than all male pu ps from any of the other diet treatments. These results suggest that m etabolic controls, functioning through endocrine mechanisms, can be al tered by changing the 20:4(n-6) to 22:6(n-3) balance in the diet.