Thyroid Function Linked to Depression

A number of studies have documented that both hypothyroidism and hyperthyroidism are associated with depression. Now, a new study in the Netherlands suggests that, in the elderly, even more subtle variations in thyroid function can also influence the risk of depression.

Researchers found that older individuals with thyroid activity at the high end of the normal range had a significantly higher risk of developing depression than those who had less thyroid activity within the normal range. The findings will soon appear in the Journal of Clinical Endocrinology & Metabolism.
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“Our results underline the strong effects of variations in thyroid function on affective behavior,” says study author Marco Medici, MD, of the Erasmus Medical Center in Rotterdam, the Netherlands. “Even minor variations in thyroid function within the normal range are an important risk factor for the development of a depressive syndrome in the elderly.”

Medici and his colleagues analyzed data from a group of about 1,500 Dutch men and women, with an average age of 70. They administered a questionnaire to assess for depression and also measured the thyroid-stimulating hormone (TSH) levels in participants at the onset of study.

Those included in the study showed no symptoms of depression at the first visit and were assessed for the development of depressive symptoms during follow-up visits over an average of 8 years.

Study participants who had more active thyroid glands were more likely to develop depression symptoms over the course of the study. The researchers did not observe any gender-specific differences.

“Although testing for overt thyroid disorders is part of the diagnostic work-up of a depression, our results suggest also a potential role for more subtle variations in thyroid function in the diagnostic work-up of a depression,” Medici says. “However, the exact implications of these subtle variations in thyroid function within the normal range for the diagnosis and treatment of a depression should be further studied in an outpatient or clinical setting."

Next, he and his colleagues plan to look at how these findings might translate to patients taking thyroid hormone replacement therapy. “It is known that a substantial part of patients on thyroxine replacement therapy still have affective complaints, despite having normal-range thyroid hormone levels,” Medici says. “In light of our findings, a next step would be to investigate if affective complaints in these patients can be improved by adjusting the dose of thyroid hormone.”

—Colleen Mullarkey

Reference

Medici M, Direk N, Visser WE, Korevaar TIM, Hofman A, Visser TJ, Tiemeier H, et al. Thyroid function within the normal range and the risk of depression: a population-based cohort study. J Clin Endocrinol Metab. doi: 10.1210/jc.2013-3589. [Epub ahead of print].