ESPE Abstracts

Aim: To determine the sensitivity, specificity of basal LH measurement compared to the GnRH test in patients with Central precocious puberty (CPP) and determine the cut off point for basal LH to diagnose CPP.

Methods: 680 female patients were referred for presumptive diagnosis of central precocious puberty in the city of Bogota. All patients went through a GnRH test, using a Roche immunoassay for Luteinizing hormone (LH) and follicle stimulating hormone (FSH). The stimulus used was triptorelin pamoate measured at 0,30,60,90,180 minutes.

Results: 680 tests of GnRH were performed. The result was positive for CPP (peak LH greater than 5 uUI/ml) in 401 patients (59%). In 114 patients (16.8%) the basal HL result was positive (>0.1 uIU/ml) with a response peak < 5 uUI/ml. In 95 (14%) patients, the basal LH was negative with a time later than 5 uIU / ml, which explains why the test was considered reactive for CPP. 306 patients (45%) had basal LH > 0.1 uIU/ml and the peak was > 5 uUI / L once, confirming the test as reactive. The sensitivity of the basal LH is 76%, specificity 59%, positive predictive value 72% and negative predictive value 65%. The sensitivity increases with a cut-off point higher than 0.7 uIU/ml of basal LH, which is 92% in patients at puberty stages Tanner 4-5.

Analysis: The diagnosis of precocious puberty requires a judicious evaluation of clinical parameters, diagnostic images such as bone age and pelvic ultrasound, and the determination of activity of the hypothalamic-pituitary-gonadal axis. With the arrival of more sensitive of gonadotropin measurements, the replacement of dynamic tests for basal measurement of gonadotropins to determine the presence of ovarian activity was proposed. This study shows how the sole measurement of gonadotropins has a low sensitivity and specificity, with high sensitivity values at puberty stages greater than Tanner 3. he measurement of basal gonadotropins has an important role in monitoring the treatment for precocious puberty but it is not considered to be a good marker for the patient with suspected precocious puberty.

Conclusion: In girls with suspition of CPP, the determination of basal LH is not a good indicator of pubertal onset in patients with suspected precocious puberty, mainly in the early pubertal stages.