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Objective: Resistance to thyroid hormone beta (RTHβ) is an inherited syndrome caused by mutations in the thyroid hormone receptor β (THRB) gene. Patients with RTHβ typically have elevated thyroid hormone levels with non-suppressed serum thyroid-stimulating hormone (TSH). We aimed to elucidate the clinical, laboratory, and imaging findings of RTHβ patients and further to explore their association with THRB gene mutations. Design and methods: We retrospectively reviewed the clinical charts and compared the clinical findings of 68 RTHβ patients (45 probands and 23 relatives) and 30 unaffected relatives in Kuma Hospital. Results: Genetic testing revealed 35 heterozygous THRB gene mutations. Among all RTHβ patients, autoimmune thyroid disease (AITD) was detected in 42.1% of men and 40.9% of women, showing that the prevalence of AITD in affected males was significantly higher than in unaffected relatives (P = 0.019). During the follow-up of 44 patients, 13 patients re (29.5%; 8 (42.1%) with AITD and 5 (20%) without AITD) temporarily showed thyroid function test results inconsistent o1 with RTHβ. Two patients with the R383H mutation, which has little dominant-negative effect, temporarily showed normal thyroid hormone and TSH levels without AITD. Conclusions: The frequency of AITD in male RTHβ patients was significantly higher compared to unaffected relatives. More than 20% of RTHβ patients temporarily showed laboratory findings atypical of RTHβ during their follow-up, and patients with AITD and specific THRB mutations were prone to display such findings. Therefore, genetic testing should be performed even for patients with fluctuations in thyroid function test results to avoid misdiagnosis and inappropriate treatment. [ABSTRACT FROM AUTHOR]

Objective: We and others recently reported that in total thyroidectomy (TT), serum triiodothyronine (T3) levels during levothyroxine (L-T4) therapy were low compared to the preoperative levels, suggesting that the presence of the thyroid tissue affects the balances of serum thyroid hormone levels. However, the effects of remnant thyroid tissue on these balances in thyroidectomized patients have not been established. Methods: We retrospectively studied 253 euthyroid patients with papillary thyroid carcinoma who underwent a TT or hemithyroidectomy (HT). We divided the cases into the TT + supplemental L-T4 (+ L-T4) group (n = 103); the HT + L-T4 group (n = 56); and the HT-alone group (n = 94). We compared the postoperative serum levels of free T4 (FT4) and free T3 (FT3) and the FT3/FT4 ratio in individual patients with those of controls matched by serum TSH levels. Results: The TT+L-T4 group had significantly higher FT4 (P<0.001), lower FT3 (P<0.01) and lower FT3/FT4 (P<0.001) levels compared to the controls. The HT+L-T4 group had FT4, FT3 and FT3/FT4 levels equivalent to those of the controls. The HT-alone group had significantly lower FT4(P<0.01), equivalent FT3 (P=0.083), and significantly higher FT3/FT4 (P<0.001) ratios than the controls. Conclusions: The presence of the remnant thyroid tissue was associated with different thyroid hormone balances in thyroidectomized patients, suggesting that T3 production by remnant thyroid tissue has a substantial effect on the maintenance of postoperative serum T3 levels. [ABSTRACT FROM AUTHOR]

OBJECTIVE: 3,5,3'-triiodothyronine-predominant Graves' disease (T3-P-GD) is characterized by a persistently high serum T3level and normal or even lower serum thyroxine (T4) level during antithyroid drug therapy. The source of this high serum T3level has not been clarified. Our objective was to evaluate the contribution of type 1 and type 2 iodothyronine deiodinase (D1 (or DIO1) and D2 (or DIO2) respectively) in the thyroid gland to the high serum T3level in T3-P-GD. METHODS: We measured the activity and mRNA level of both D1 and D2 in the thyroid tissues of patients with T3-P-GD (n=13) and common-type GD (CT-GD) (n=18) who had been treated with methimazole up until thyroidectomy. RESULTS: Thyroidal D1 activity in patients with T3-P-GD (492.7±201.3 pmol/mg prot per h) was significantly higher (P<0.05) than that in patients with CT-GD (320.7±151.9 pmol/mg prot per h). On the other hand, thyroidal D2 activity in patients with T3-P-GD (823.9±596.4 fmol/mg prot per h) was markedly higher (P<0.005) than that in patients with CT-GD (194.8±131.6 fmol/mg prot per h). There was a significant correlation between the thyroidal D1 activity in patients with T3-P-GD and CT-GD and the serum FT3-to-FT4ratio (r=0.370, P<0.05). Moreover, there was a strong correlation between the thyroidal D2 activity in those patients and the serum FT3-to-FT4ratio (r=0.676, P<0.001). CONCLUSIONS: Our results suggest that the increment of thyroidal deiodinase activity, namely D1 and especially D2 activities, may be responsible for the higher serum FT3-to-FT4ratio in T3-P-GD. [ABSTRACT FROM AUTHOR]