[Vitamin A and carotene in thyroid diseases]

From 190 goitrous patients (106 euthyroid, 53 hyperthyroid, 31 hypothyroid) serum levels of vitamin A and carotene were obtained. The serum levels of vitamin A were significantly decreased in both hyperthyroidism and hypothyroidism, the serum levels of carotene in hypothyroidism only. Remarkably, vitamin A levels almost never drop to subnormal values in hyperthyroidism. There is evidence, that a sufficient dietary protein supply enables the liver cell to produce enough amounts of retinol binding protein and prealbumin to overcome the increased clearance observed in hyperthyroid conditions.