Abstract
BackgroundLow-normal thyroid function within the euthyroid range may contribute to increased atherosclerosis susceptibility. The leptin/adiponectin (L/A) ratio is associated with cardiovascular disease and reflects adipose tissue dysfunction. Relationships of the L/A ratio with low-normal thyroid function are unknown.MethodsRelationships of thyroid stimulating hormone (TSH) and free thyroxine (free T4) with leptin, adiponectin and the L/A ratio in euthyroid subjects were documented in 67 fasting subjects with metabolic syndrome (Mets) and 86 euthyroid subjects without MetS (TSH and free T4 levels within the institutional reference range).ResultsNeither plasma leptin nor adiponectin was significantly correlated with TSH or free T4 in subjects with and without MetS. In the whole group, high sensitivity C-reactive protein (hs-CRP) was positively correlated with the L/A ratio (r = 0.485, P < 0.001). Notably, the L/A ratio was positively correlated with TSH in subjects with MetS (r = 0.252, P = 0.040) but not in subjects without MetS (r = −0.068, P = 0.54; interaction term, P = 0.027). In MetS subjects, the L/A ratio remained positively related with TSH after adjustment for age, sex, diabetes status, hs-CRP and the use of antihypertensive and glucose lowering medication (β = 0.283, P = 0.018), as well as after adjustment for individual MetS components (β = 0.294, P = 0.020).ConclusionsIn the context of MetS, a higher TSH within the euthyroid range confers an increased L/A ratio, a proposed marker of atherosclerosis susceptibility and adipocyte dysfunction.
Highlights
Low-normal thyroid function within the euthyroid range may contribute to increased atherosclerosis susceptibility
The concept is emerging that low-normal thyroid function, as inferred from a higher thyroid stimulating hormone (TSH) or a lower free thyroxine within the euthyroid range, may adversely impact several health issues including the development of cardiovascular disorders [1, 2]
These findings provide a rationale to hypothesize that the plasma leptin/adiponectin (L/A) ratio is higher in subjects with low-normal thyroid function
Summary
Low-normal thyroid function within the euthyroid range may contribute to increased atherosclerosis susceptibility. The concept is emerging that low-normal thyroid function, as inferred from a higher thyroid stimulating hormone (TSH) or a lower free thyroxine (free T4) within the euthyroid range, may adversely impact several health issues including the development of cardiovascular disorders [1, 2] In line with this concept, low-normal thyroid function is associated with a greater increased intima media thickness (cIMT), an established biomarker of subclinical atherosclerosis [3, 4]. Leptin has been reported to van Tienhoven-Wind and Dullaart Lipids in Health and Disease (2017) 16:6 decrease and adiponectin to increase after levothyroxine supplementation in subclinical hypothyroidism [16] These findings provide a rationale to hypothesize that the plasma leptin/adiponectin (L/A) ratio is higher in subjects with low-normal thyroid function. The L/A ratio is elevated in MetS [21,22,23], which supports the potential clinical relevance to determine relationships of low-normal thyroid function with the L/A ratio in subjects with MetS
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