The effects of cold exposure on serum total T4 (TT4), total T3 (TT3), free T4 (FT4), free T3 (FT3), rT3, TSH, T4-binding globulin (TBG), and T3 resin uptake were investigated in 82 euthyroid factory workers. Twenty-five workers (group 1) were exposed intermittently (approximately 3.5 h daily) to extreme cold (-40 to -20 C) during the 8-h work shift, and 47 (group 2) were exposed to moderate cold (-10 to 8 C) for the entire 8 h. Ten individuals working at room temperature for the same period also were studied. After cold exposure, serum TT4 decreased in group 1 and did not change in group 2, whereas FT4 did not change in group 1 and increased in group 2. After exposure, serum TT3 and rT3 decreased significantly in both groups, while FT3 did not change in either. The basal serum TT4 levels in groups 1 and 2 were significantly lower than those in the control group, whereas those of FT4 and FT3 were higher. Thus, cold exposure had opposite effects on total thyroid hormones and their free fractions, consistent with a cold-induced decrease in thyroid hormone-binding capacity. A postexposure decrease in serum TBG was found in women in group 2, but not in men in either group 2 or group 1, suggesting that factors other than decreased TBG are also involved. The results suggest the possibilities that 1) decreased thyroid hormone-binding capacity is an adaptive response to cold exposure, and/or 2) increased free thyroid hormone levels in response to cold exposure result in a new higher equilibrium between extracellular and intracellular FT4 and FT3.

Despite some reports, the usefulness of levothyroxine (LT(4)) and levotriiodothyronine (LT(3)) combination therapy in hypothyroidism remains controversial. The objective of this paper is to study a benefit of additional LT(3) in athyreotic patients who failed to normalize TSH on LT(4) alone even with hyperthyroid serum T(4) values. In a survey of 200 athyreotic patients treated between 2006 and 2009, about 7% failed to normalize serum TSH levels following treatment with LT(4), though serum T(4) values in the hyperthyroid range were achieved. These patients (characterized by serum T(4)≥160 nmol/L and TSH≥5.0 mIU/L), were additionally treated with 10 μg b. i. d LT(3). LT(3) and LT(4) combination therapy resulted in decreased serum TSH levels into the normal range (12.8 vs. 1.22 mIU/L; p<0.01) and reduced LT(4) dose (153.3 vs. 117.5 μg; p<0.01) required for normalization of serum T(4) values (170.6 vs. 123.3 nmol/L; p<0.01). Serum T(3) values were higher (1.3 vs. 2.26 nmol/L; p<0.01) than those during monotherapy with LT(4). Our results indicate a subpopulation of athyreotic patients that could significantly benefit from combined LT(4) + LT(3) therapy in restoring normal TSH and thyroid hormone patterns. Further research should be undertaken to provide a genetic basis for these findings.

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Initially, higher methimazole doses with rapid progressive decrease to maintenance dose result in similar remission rates and are followed by similar incidence of adverse side-effect as fixed low dose therapy. Our results indicate that neither an early restoration of euthyroidism nor the difference in methimazole doses influence the course of Graves' disease.

Six nodular tissues of non-treated and four of treated patients (suppressive treatment with thyroid hormones from three months to two years until the operation) with nodular non-toxic goitre contained low T3 (less than 1 ug/g w.w.). The results of iodothyronines and thyroglobulin (Tg) were compared with respective tissues containing T3 greater than 1 ug/g w.w. In non-treated patients, nodular tissues with low T3 and very high T4/T3 ratio showed T4 and Tg concentrations not different from the tissues with T3 greater than 1 ug/g w.w. In the goitres with low T3 of treated patients, T4 was also reduced but disproportionately to T3. Microscopically, nodular goitres with low T3 were characterized with gross fibrous infiltration and diffuse haemorrhage which was substantially different from histological findings in nodular goitres with T3 greater than 1 ug/g w.w. High T4/T3 ratio in the tissues with low T3 is similar to increased T4/T3 ratio in paranodular tissues of autonomously functioning adenomas. The results suggest that low T3 and high T4/T3 ratio in nodular goitrous tissue could be due to grossly impaired thyroid function or due to suppressed secretion of TSH.