Hypothyroidism: an early sign of vitamin A deficiency in chickens.
The effect of a marginal vitamin A deficiency on thyroid function was investigated in chicks gaining weight. This study examined the hypothesis that hypothyroidism is one of the earliest manifestations of hypovitaminosis A in chicks. Day-old Leghorn cockerels were fed vitamin A-adequate and deficient diets. Blood vitamin A levels were reduced in the deficient chicks by 3 weeks of age. Body weight gains were less in the 5-, 6-, 7- and 8-week-old A-deficient chicks than in controls. Compared to controls, vitamin A-deficient chicks were characterized by thyroid follicle hypertrophy by 4 weeks, heavier thyroids as a percent of body weight at 5 weeks, less serum thyroxine (T4) at 7 weeks and lower serum triiodothyronine (T3) and T4 at 8 weeks. These results indicate that one of the earliest signs of vitamin A deficiency in chicks is hypothyroidism.
D000818:Animals; D002645:Chickens / Q000097:blood*; D007037:Hypothyroidism / Q000097:blood / Q000209:etiology / Q000662:veterinary*; D008297:Male; D009929:Organ Size; D011201:Poultry Diseases / Q000097:blood*; D013961:Thyroid Gland / Q000473:pathology; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D014802:Vitamin A Deficiency / Q000097:blood / Q000150:complications / Q000662:veterinary*
D014284:Triiodothyronine; D013974:Thyroxine