Yonago Acta medica 1996;39:177–182
A Patient with Graves’ Hyperthyroidism Associated with Non-Insulin Dependent Diabetes Mellitus Who Showed T4-Toxicosis
Sachiko Teshima, Koushi Narasaki, Yasushi Tanaka, Akio Yoshida and Chiaki Shigemasa
First Department of Internal Medicine, Faculty of Medicine, Tottori University, Yonago 683, Japan
A 41-year-old man was admitted to Tottori University Hospital because of a very poor control state of diabetes mellitus (DM). At admission, he showed T4-toxicosis [T4 13.4 µg/dL, free T4 (FT4) 3.0 ng/dL, T3 105 ng/dL, and free T3 (FT3) 2.7 pg/mL] with a high reverse T3 (rT3; 189 ng/dL) and a high thyroid 99mTcO4--uptake (8.0%), and did not show apparent physical findings suggestive of hyperthyroidism except for a diffuse goiter. After the initiation of diet and insulin therapy for DM, his serum FT3 level was gradually increased despite a slight decrease in his serum FT4 level, and reached a supra-normal level (5.4 pg/mL) on the 35th day after admission. In this interval, he became to show apparent physical findings suggestive of hyperthyroidism, such as tachycardia, moist skin, finger tremor and a decrease in diastolic blood pressure. Both serum FT4 and FT3 levels were in normal ranges 3 weeks after the initiation of methimazole therapy. Thus, the patient with Graves’ hyperthyroidism associated with a very poor control state of DM may show T4-toxicosis, which is induced by the inhibition of extrathyroidal conversion of T4 to T3. Such a patient may not show apparent physical findings suggestive of hyperthyroidism owing to normal FT3 level and probably owing to the diminished T3-binding to the T3 receptor and/or post-T3 receptor responses.
Key words: diabetes mellitus; Graves’ hyperthyroidism; T4-toxicosis
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