Reduced active thyroid hormone levels after delivery.

The effect of delivery on the serum concentration of thyroid hormones was studied in 25 euthyroid women. After delivery serum free and total T3 and T4 fell transiently with a simultaneous increase in reverse T3 while serum TSH and thyroxine binding globulin (TBG) concentrations showed no significant variation. These data suggest that i) similar to what happens in other stressful situations, delivery influences peripheral T4 metabolism, and ii) an elevation of TBG in serum in the early puerperium does not prevent these changes.