Early onset of lithium-associated hypothyroidism.

In general practice, psychiatrists are confronted with the difficulty of structuring a rational design for the early detection of hypothyroidism. To determine the period during which a patient receiving lithium is most at risk of developing hypothyroidism, a retrospective study was conducted on the records of 154 patients at two general hospital lithium clinics from January 1980 to August 1991. Forty-two cases of hypothyroidism (clinical hypothyroidism and/or abnormally elevated levels of TSH) were detected. A significant difference was found between the onset of hypothyroidism and age (older patients developed more thyroid dysfunction), but no significant differences were found between thyroid abnormality and sex or diagnostic category and menopausal status, although trends were observed for the two former variables. This longitudinal study is the first to describe an outline of thyroid functioning in terms of the duration of treatment. Lithium-associated hypothyroidism develops most often during the first two years. Of the 42 cases of hypothyroidism, 16 were diagnosed within six months (38%), 23 within the first year (55%), and 31 two years (74%). Since thyroid functioning is an important parameter in the course of affective disorders, its close and frequent monitoring is mandatory during the first two years of treatment.