Key result
Active brown adipose tissue was associated with significantly higher TSH levels in thyroidectomized patients compared to matched controls with non-active BAT (P<0.05).
Why the study?
Does hypothyroidism increase brown adipose tissue activity compared to euthyroidism?
Case-Control (n=124)
Does hypothyroidism increase brown adipose tissue activity compared to euthyroidism?
p-value: p=<0.05
Hypothyroidism is associated with increased brown adipose tissue activity, likely as a feedback mechanism to maintain body temperature.
Association between active BAT and higher TSH warrants no practice change; leaves open causal role of hypothyroidism in BAT activation.
BACKGROUND: Brown adipose tissue (BAT) attracts growing interest as a potential therapeutic target for obesity and diabetes. Hyperthyroidism is well-known to increase BAT activity, but the role of hypothyroidism is controversial. We aimed to investigate the association between different thyroid hormone (TH) states and BAT activity. METHODS: FDG-PET studies were retrospectively evaluated in thyroid cancer patients after total thyroidectomy both at euthyroidism during TH replacement or at hypothyroidism after TH cessation. Serum TH levels were compared between patients with active BAT and control patients with non-active BAT matched for age, gender, and body mass index. Additionally, animal experiments with controls (n = 5) and hypothyroid rats (n = 5) were performed. RESULTS: Out of 124 patients, 6 patients with active BAT were identified. These patients showed significantly higher thyroid-stimulating hormone (TSH) levels than matched controls (P < 0.05). In animal experiments, all hypothyroid animals showed BAT activation at room temperature (24 °C), whereas controls did not (P < 0.001). Increased BAT activity was also confirmed by increased expression of UCP-1 and D2. CONCLUSIONS: Increased BAT metabolism appears to be related with hypothyroidism, which might be the result of a feedback mechanism to maintain body temperature in a state of reduced basal thermogenesis. Future research needs to explore the underlying mechanistic and biological implications.
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Lapa et al. (2015) conducted a case-control in Thyroid cancer (n=124). Active brown adipose tissue (BAT) vs. Non-active BAT was evaluated on Thyroid-stimulating hormone (TSH) levels (p=<0.05). Active brown adipose tissue was associated with significantly higher TSH levels in thyroidectomized patients compared to matched controls with non-active BAT (P<0.05).