Abstract
BackgroundAlthough depression is associated with changes in the hypothalamic-pituitary-thyroid axis, its relationship with subclinical hypothyroidism (SCH) is controversial. To date, there is a lack of data on the improvement of depressive symptoms with levothyroxine therapy among individuals with coexistent SCH.MethodsWe conducted a meta-analysis to evaluate the association between SCH and depression including 1) the prevalence of depression in SCH (with a sub-analysis of the geriatric cohort), 2) thyroid stimulating hormone (TSH) level among patients with depression and 3) the effect of levothyroxine therapy among patients with SCH and coexistent depression.ResultsIn a pooled analysis of 12,315 individuals, those with SCH had higher risk of depression than euthyroid controls (relative risk 2.35, 95% confidence intervals [CI], 1.84 to 3.02; p < 0.001). Geriatric cohort with SCH had a 1.7-fold higher risk of depression compared with healthy controls (odds ratio 1.72, CI, 1.10 to 2.70; p = 0.020). There was no difference in the mean TSH level between individuals with depression and healthy controls (2.30 ± 1.18 vs. 2.13 ± 0.72 mIU/L, p = 0.513). In individuals with SCH and coexistent depression, levothyroxine therapy was neither associated with improvement in the Beck Depression Inventory scoring (pooled d + = − 1.05, CI -2.72 to 0.61; p = 0.215) nor Hamilton Depression Rating Scale (pooled d + = − 2.38, CI -4.86 to 0.10; p = 0.060).ConclusionSCH has a negative impact on depression. Early and routine screening of depression is essential to prevent morbidity and mortality. However, the use of levothyroxine among patients with SCH and coexistent depression needs to be individualized.
Highlights
Depression is associated with changes in the hypothalamic-pituitary-thyroid axis, its relationship with subclinical hypothyroidism (SCH) is controversial
Thyroid hormones which are widely distributed in the central nervous system, regulate the neuronal growth and form synapses
SCH is defined as an elevated thyroid stimulating hormone (TSH) with normal Free thyroxine (fT4) and Free triiodothyronine (fT3) levels
Summary
Depression is associated with changes in the hypothalamic-pituitary-thyroid axis, its relationship with subclinical hypothyroidism (SCH) is controversial. SCH is defined as an elevated thyroid stimulating hormone (TSH) with normal fT4 and fT3 levels It affects 3 to 8.5% of the general population with a female preponderance, and a higher rate up to 20% among elderly people [7, 8]. Its association with depression remains controversial at large, with some studies indicated that SCH had the same propensity with overt hypothyroidism, while the others reported conflicting findings [7, 8, 12,13,14,15,16,17,18,19,20,21,22,23,24] These inconsistent results could be attributed to the heterogeneous study populations, small sample size, lack of control arm for comparison and differences in study design
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