Lithium-associated clinical hypothyroidism - Prevalence and risk factors

Background Rates of, and risk factors for, lithium-associated clinical hypo thyroidism are uncertain. Aims To determine prevalence of and risk factors for clinical hypothyroidis m in patients treated with lithium carbonate. Method Retrospective case-note review of 718 patients who had undergone ser um lithium estimation during a 15-month period. Patients on thyroxine had a more detailed review. Results The prevalence of clinical hypothyroidism during lithium treatment was 10.4%. The main risk factor was female gender (women 14% v. men 4.5%). Women were at highest risk during the first two years of lithium treatment, and women starting lithium aged 40-59 years had the greatest prevalence (> 20%). No equivalent risk factors emerged in men, although, like women, thei r prevalence of hypothyroidism was substantially higher than community rate s. Conclusions The high rates of clinical hypothyroidism identified may call f or a review of the drug information given to women, particularly to those s tarting lithium in middle age. Consideration should be given to screening f or thyroid antibodies before treatment in high-risk cases. Monitoring of th yroid function should take into account gender, age and stage of lithium tr eatment. Declaration of interest None.