Triiodothyronine and thyroxine in human, cow's and formula milk.

Triiodothyronine concentration in extracted human, cow's and formula milk was measured. The highest concentration (mean +/- SD = 1.56 +/- 1.34 nmol/l) was found in cow's milk and lowest (0.99 +/- 0.38 nmol/l) in formula milk. Thyroxine was not detected in any sample of milk. The scatter of obtained values for T3 was highest also in cow's milk. It seems possible that milk from same cows may to certain extense mitigate neonatal hypothyreoidism.