Effects of a large dose of retinol or retinoic acid on the thyroid hormones in the rat.

The daily food intake of a large dose of retinol (as palmitate) or retinoic acid (as all-trans retinoic acid) modifies numerous parameters of the thyroidal status in the rat. There were decreases of the serum total thyroxine (TT4) and triiodothyronine (TT3), and of the biological half-life of T4, while there were increases of the dialyzable fractions of T4 and T3 and of the apparent distribution space of T3. The possible causes of these changes are discussed.