In the Journals Plus

Depression unrelated to subclinical hypothyroidism

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February 8, 2018

Middle-aged men and women with subclinical hypothyroidism are no more likely to experience incident depression than adults without the condition, according to an analysis of the Samsung Health Study cohort.

“Although a previous meta-analysis showed a possible link of thyroid function with incident depression among middle-aged men, the role of subclinical hypothyroidism in the development of depression remains controversial,” Ji Sun Kim, of the Workplace Mental Health Institute at Kangbuk Samsung Hospital in Seoul, South Korea, and colleagues wrote. “Additionally, the effectiveness of thyroid hormone supplementation in the treatment of depression remains controversial, with some positive but also some null studies.”

Kim and colleagues analyzed data from 92,206 South Korean men and women without clinically significant depressive symptoms and free of overt hypothyroidism or subclinical hyperthyroidism, who underwent at least two health exams between 2011 and 2014 as part of the Kangbuk Samsung Health Study (32.7% women; mean age, 40 years). Researchers measured levels of serum thyroxine (normal range, 0.93-1.7 ng/dL), free triiodothyronine (normal range, 2-4.4 pg/mL), and thyroid-stimulating hormone (normal range, 0.25-5 µIU/mL). Clinically significant depression was defined as a score of at least 16 on the Korean version of the Center for Epidemiologic Studies Depression Scale. Researchers followed the cohort from baseline visit to either visit of development of depressive symptoms or last available visit, and they compared the risk for incident depression among patients with and without subclinical hypothyroidism. Researchers also assessed the dose-response relationship between thyroid hormone levels and depressive symptoms among euthyroid patients.

Within the cohort, average levels of TSH, free T4 and free T3 were 2.2 µIU/mL, 1.3 ng/dL and 3.2 pg/mL, respectively; 4,384 patients had subclinical hypothyroidism. During a median follow-up of 2 years, 7,323 patients experienced incident depressive symptoms.

In comparing patients with subclinical hypothyroidism with euthyroid patients, the adjusted HR for incident depressive symptoms was 0.95 (95% CI, 0.85-1.06). Results persisted after further adjustment for stress levels (HR = 0.97; 95% CI, 0.87-1.09).

Among patients with subclinical hypothyroidism, 7% had a TSH level of at least 10 mU/L.

Researchers similarly did not observe an association between thyroid hormone levels and increased risk for incident depression in euthyroid patients. In comparing the highest with lowest quartiles, the adjusted HR for incident depression among euthyroid patients were 0.92 for TSH (95% CI, 0.86-0.99), 0.97 for free T4 (95% CI, 0.9-1.05) and 1 for free T3 (95% CI, 0.92-1.08), according to researchers. – by Regina Schaffer

Disclosures: The authors report no relevant financial disclosures.