Prevalence and determinants of thyroid disorders in elderly patients with affective disorders: lithium and nonlithium...

To determine the prevalence and determinants of thyroid dysfunction in older patients with affective disorders divided into lithium and nonlithium patients.

This study was conducted as a retrospective cross-sectional study in patients of 65 years and older with affective disorders according to Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria. The presence of thyroid disorders was determined on the index date defined as the date of the first available thyroid-stimulating hormone in 2005. The presence of thyroid disorder was diagnosed according to defined criteria and in case of a previous diagnosis, confirmed by researching the medical files. In a subgroup of 45 lithium patients, thyroperoxidase- and thyroglobulin antibodies were determined.

A total of 79 lithium patients and 85 nonlithium patients were included. The prevalence of hypothyroidism (subclinical and clinical) was 35.4% among the lithium patients, with women having a prevalence as high as 41.3% and men 12.6%. In the nonlithium patients, the prevalence was 7.1%; very close to that in the general population. No other determinant than female gender was identified. Seventeen of the 26 lithium patients were diagnosed with hypothyroidism in the first 31/2 years after the start of lithium. The prevalence of thyroid antibodies was 27% in 45 lithium patients, which was no different than the prevalence in the same age group in the general population.

The prevalence of hypothyroidism during lithium treatment was very high in the elderly, especially in women. Autoimmunity did not seem to play a major part in lithium-associated hypothyroidism in this age group. The timeframe between start of lithium and diagnosis of hypothyroidism suggests an individual susceptibility. The prevalence of hypothyroidism in nonlithium patients with affective disorders was not very different from the general population.