Sexual differences in serum free amino acid levels in thyropathies.

Changes in serum free amino acid level with respect to sex and thyroid function are described. In euthyroid men, the amount of total, glucogenic, essential and nonessential amino acids is significantly higher than in euthyroid women. Patients with thyrotoxicosis exhibited increased levels of all main groups of free amino acids in blood serum. However, the sex-related differences in the main amino acids groups disappeared. The hypothyroidism was also accompanied by the disappearance of the sexual differences between the individual amino acids. The content of essential amino acids declined both in hypothyroid males and females. The participation of metabolic alterations of androgens and estrogens accompanying thyropathies in the genesis of sex-linked amino acid changes is discussed.