Clinical and Biochemical Factors Associated with GnRH Stimulation test in the Idiopathic Central Precocious Puberty and Early Puberty Girls

Abstract

Purpose: Gonadotropin releasing hormone (GnRH) stimulation test is the gold standard method for the diagnosis of central precocious puberty. To predict the result of this test, we studied clinical and biochemical factors associated with the test.

Methods: We evaluated 168 girls under 9 years old with the signs of breast budding and more than one year bone age advancement who underwent this test. We defined the result as two criteria. In the first criteria, positive result of the test means peak LH≥5 IU/L and peak/basal LH≥2. In the second criteria, positive result means peak LH≥5 IU/L, peak/basal LH≥2 and peak LH/FSH≥1.

Results: In the both first and second criteria, 83 and 31 girls had positive results and other 85 and 137 girls had negative results respectively. In both criteria, the patients with positive results turned out to have more advancement in bone age, smaller predicted adult height, smaller paternal height and higher insulin like growth factor-1 (IGF-1) than those of the patients with negative results. Peak LH was positively correlated with bone age advancement (r=0.35, P<0.001) and IGF-1 (r=0.42, P<0.001) and negatively correlated with predicted adult height (r=-0.22, P=0.01). In multiple logistic regression, bone age was significant predictive factor [first criteria, OR 1.43 (95% CI 1.09, 1.87), P=0.01; second criteria, OR 2.46 (95% CI 1.48, 4.08), P=0.01] of the positive results.

Conclusion: The result of GnRH stimulation test depends on the degree of breast development and advancement in bone age. Also, IGF-1 is the only positively correlated biochemical factor with the test.