Mental and physical state in subclinical hyperthyroidism: investigations in a normal working population

We investigated whether subclinically hyperthyroid individuals selected from a nonpatient working population exhibit similar impairments to those found in studies with patients. Sixteen subclinically hyperthyroid subjects without apparent reason (SH-0) and 15 subclinically hyperthyroid subjects on levothyroxine (SH-T4) were compared with 27 euthyroid controls with respect to signs and symptoms of hyperthyroidism, sleep, depressivity, ability to concentrate, anxiety, and other dimensions of well-being. We found that SH-T4 exhibited significantly higher TT4 levels, TT4/TBG ratios, and more palpitations than controls. Furthermore, they slept less. The SH-0 subjects reported being in a better mood and less touchy than controls. Psychometric results of all groups were within the normal range. A comparison of this study to previous studies reveals that TT4 levels or TT4/TBG ratios may play a crucial role in the development of the predominantly nervous symptoms in subclinical hyperthyroidism. Possible reasons for the discrepancies between results in hospital and nonhospital settings are discussed.