(HealthDay News) — Low-normal thyroid stimulating hormone (TSH) is a risk factor for depression in the elderly, according to a study published online February 24 in the Journal of Clinical Endocrinology & Metabolism.

Marco Medici, MD, from the Erasmus Medical Center in Rotterdam, Netherlands, and colleagues assessed the correlation between normal-range thyroid function and the risk of depression in a cohort of 1,503 Dutch men and women (mean age, 70.6 years). Serum TSH, thyroperoxidase antibody levels, and depressive symptoms (Center for Epidemiologic Studies Depression Scale [CES-D]) were assessed at baseline. The occurrence of incident depressive syndromes was monitored during a mean follow-up of eight years.

The researchers found that 156 participants developed depressive syndromes. Compared with participants in the highest normal-range TSH tertile (1.6–4.0 mU/L), participants in the lowest TSH tertile (0.31.0mU/L) had more depressive symptoms (mean CES-D score, 7.95 vs. 6.63; P=0.014) and had an elevated risk of a CES-D score of 16 or greater (odds ratio, 2.22), indicative of a depressive disorder. Those who were depression free and in the lowest TSH tertile at baseline had an increased risk of incident depressive syndromes (odds ratio, 1.85). There was no correlation between thyroid autoimmunity (thyroperoxidase antibody positivity) and CES-D scores or incident depressive syndromes.

“This study identifies low-normal TSH as an important risk factor for depression in the elderly,” the authors write.

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