The effect of thyroidectomy on the pattern of fatty acids synthesized by mammary gland from lactating rats.

Thyroidectomy decreased the content of short-chain fatty acids and increased the content of long-chain fatty acids in the mammary glands of lactating rats. This effect was replicated in the glands of untreated rats limited to the same food intake as the thyroidectomized animals. Thyroidectomy decreased the incorporation of [6-(14)C]glucose into short-chain fatty acids and increased the incorporation into longer-chain acids. Restriction of the food intake of untreated animals did not cause a similar shift of the incorporation pattern. The possibility that the thyroxine effect on lipogenesis is secondary to its effect on carbohydrate metabolism is discussed.