Thyrotropin, free and total triiodothyronine, and thyroxine in serum during surgery.

Changes in free and total thyroxine (T4), triiodothyronine (T3) and thyroid stimulating hormone (TSH) in serum were measured before, during, and for nine days after uncomplicated abdominal surgery in eight patients. The results showed a pronounced fall in total as well as in free T3 levels, amounting to 50% in both variables on the first postoperative day, and returning towards preoperative levels on the seventh and ninth day. Apart from an increase during surgery, free T4 levels were constant in the whole period despite a slight postoperative decrease in total T4. The TSH level fell about 80% within the first 24 postoperative h, but returned to the preoperative level thereafter. These results suggest a suppression of both T3 and TSH production during the pre- and early postoperative period.