Thyroid function in pyridoxine-deficient young rats.

In pyridoxine-deficient young rats hypothalamic serotonin was decreased with no changes in the dopamine and noradrenaline content. Serum thyroxine and tri-iodothyronine concentrations were much lower in the deficient rats as compared to pyridoxine-supplemented controls. No significant difference between deficient and control groups in the serum TSH concentration was detected. Highly significant decreases in the content of pituitary TSH and in the number of pituitary thyrotroph secretory granules were found. These results suggest that the hypothyroidism of pyridoxine-deficient young rats might be of hypothalamic origin.