ABSTRACT
PURPOSE: Obesity is a well-known risk factor for central precocious puberty (CPP). Recently, elevated thyroid stimulating hormone (TSH) was reported in obese youth. However, few data regarding the relationship between CPP and TSH are available. The aim of this study was to evaluate thyroid function in girls with CPP and the relationship between CPP and serum TSH concentration. METHODS: This was a retrospective cross-sectional study. A total of 1,247 girls aged between 6.0 and 8.9 years who had undergone a gonadotropin-releasing hormone (GnRH) stimulation test to determine the presence of puberty were studied. Subjects were classified into CPP (n=554) and non-CPP (n=693) groups according to the results of the GnRH stimulation test. Characteristics and laboratory data of the CPP and non-CPP groups were compared and correlations between those characteristics and laboratory data and TSH concentration were evaluated. Serum TSH concentration in the CPP group was higher than that of the non-CPP group (3.19±1.55 mIU/L vs. 2.58±1.34 mIU/L, P<0.001). RESULTS: Serum free thyroxine (fT4) concentration in the CPP group was notably lower than that of the non-CPP group (1.38±0.14 ng/dL vs. 1.44±0.18 ng/dL, P<0.001). Across all subjects, 149 girls (11.9%) had hyperthyrotropinemia. The prevalence of hyperthyrotropinemia was higher in the CPP group compared to the non-CPP group (15.7% vs. 8.9%, P<0.001). TSH concentrations were positively correlated with age, height, weight, BMI, bone age, bone age advance, insulin-like growth factor 1 (IGF-1), IGF-1 standard deviation score, basal luteinizing hormone (LH), peak LH and basal follicle-stimulation hormone. TSH concentrations were negatively correlated with fT4. Multiple linear regression analysis showed that age (ß=0.548, P<0.001) and peak LH (ß=0.019, P=0.008) were independently associated with serum TSH concentration. CONCLUSION: Hyperthyrotropinemia in girls with CPP tends to be associated with pubertal LH elevation. In conclusion, pubertal onset may be associated with thyroid function.
ABSTRACT
Osteocalcin is the non-collagenous protein produced by osteoblasts in bone. When it is released into systemic circulation in its uncarboxylated form, it regulates fat and glucose metabolism. Recent studies have shown that osteocalcin is also involved in male fertility. Because the onset of puberty is determined by ethnic, genetic, environmental, and metabolic factors, we focused on determining the role of osteocalcin in the onset of puberty. Central precocious puberty (CPP) is defined as the activation of the hypothalamic-pituitary-gonadal axis before the age of 8 in girls and 9 in boys. CPP is diagnosed when peak luteinizing hormone (LH) reaches ≥ 5.0 IU/l after stimulation with gonadotropin-releasing hormone (GnRH). This retrospective study included 206 girls who showed breast budding before the age of 8 and whose bone age was more advanced than their chronological age. The CPP group included 100 girls who were diagnosed with CPP, and 106 girls were the non-CPP group whose peak LH did not reach ≥ 5.0 IU/l after GnRH stimulation test. Serum osteocalcin levels were measured to investigate the relationship between osteocalcin and the onset of puberty. Our data showed that serum osteocalcin levels were significantly higher in the CPP group (87.7 ± 24.4 ng/ml vs. 68.3 ± 19.5 ng/ml, P < 0.001). The multivariate analysis revealed that an increase in bone age and peak LH was significantly associated with the serum osteocalcin level. The results of this study suggest that serum osteocalcin is associated with the onset of puberty in girls.
