Early hypothyroidism after subtotal thyroidectomy in patients with Graves' disease--the role of the preoperative conservative treatment and hormonal status

AIM: The aim of the present study was to evaluate the role of the preoperative antithyroid drug treatment and hormonal status in the development of early postoperative hypothyroidism after subtotal thyroidectomy in patients with Graves' disease. MATERIAL AND METHODS: Eighty-five patients with Graves' disease (males : females ratio 1:5.54, age range 19 to 64, 37.52 +/- 1.09 yrs) who had previously undergone surgical treatment were enrolled in the study. All patients underwent bilateral subtotal thyroidectomy with the amount of remnant tissue of 2-3 g for each lobe (total 4-6 g). Development of early (within one year after the operation) postoperative hypothyroidism was analyzed regarding the type of the antithyroid drug, preoperative dose, duration of the preoperative medical treatment, FT3, FT4, FT3/FT4 and hTSH. RESULTS: Forty six percent of all examined patients (54.12%) were euthyroid and 39 (45.88%/)--hypothyroid. Postoperative hypothyroidism was developed by 33.33% of the patients that had received preoperatively propylthiouracil compared with 50.82% of those treated with methymazol (p > 0.05). The duration of the preoperative treatment was 38.36 +/- 3.53 months for the hypothyroid patients and 30.11 +/- 2.34 months for the euthyroid patients (p < 0.05). Postoperative hypothyroidism developed in 58.70% of the patients with preoperatively suppressed thyroid-stimulating hormone (hTSH) and in 33.33% of those with normalized values of hTSH (p < 0.05). No statistically significant between-group difference was found in the preoperative dose of antithyroid agent, mean values of free triiodothyronine (FT3), free thyroxine (FT4), FT3/FT4, thyrotropic hormone (TSH). CONCLUSIONS: Longer preoperative antithyroid drug treatment and suppression of hTSH in the preoperative period correlated with higher risk of hypothyroidism after subtotal thyroidectomy. The type and the preoperative dose of the antithyroid agent, as well as the mean values of thyroid hormones before the operation have no prognostic significance for postoperative thyroid hypofunction.