BACKGROUND: Obesity is known to be associated with higher risks of 
cardiovascular disease, metabolic syndrome, and diabetes mellitus. 
Thyroid-stimulating hormone (TSHR) is the receptor for thyroid-stimulating 
hormone (TSH, or thyrotropin), the key regulator of thyroid functions. The 
expression of TSHR, once considered to be limited to thyrocytes, has been so far 
detected in many extrathyroidal tissues including liver and fat. Previous 
studies have shown that TSHR expression is upregulated when preadipocytes 
differentiate into mature adipocytes, suggestive of a possible role of TSHR in 
adipogenesis. However, it remains unclear whether TSHR expression in adipocytes 
is implicated in the pathogenesis of obesity.
METHODS: In the present study, TSHR expression in adipose tissues from both mice 
and human was analyzed, and its association with obesity was evaluated.
RESULTS: We here showed that TSHR expression was increased at both mRNA and 
protein levels when 3T3-L1 preadipocytes were induced to differentiate. 
Knockdown of TSHR blocked the adipocyte differentiation of 3T3-L1 preadipocytes 
as evaluated by Oil-red-O staining for lipid accumulation and by RT-PCR analyses 
of PPAR-γ and ALBP mRNA expression. We generated obesity mice (C57/BL6) by 
high-fat diet feeding and found that the TSHR protein expression in visceral 
adipose tissues from obesity mice was significantly higher in comparison with 
the non-obesity control mice (P < 0.05). Finally, the TSHR expression in adipose 
tissues was determined in 120 patients. The results showed that TSHR expression 
in subcutaneous adipose tissue is correlated with BMI (body mass index).
CONCLUSION: Taken together, these results suggested that TSHR is an important 
regulator of adipocyte differentiation. Dysregulated expression of TSHR in 
adipose tissues is associated with obesity, which may involve a mechanism of 
excess adipogenesis.