A single-sample, subcutaneous gonadotropin-releasing hormone test for central precocious puberty

Objective. We compared a rapid,subcutaneous (SQ), single-sample gonadotropin-releasing hormone (GnRH) stimulation test with the standard multiple-sample, intravenous (IV) GnRH stimulation test used in the evaluation of central precocious puberty (CPP). Methods. We evaluated 22 patients presenting with evidence of precocious puberty, GnRH (100 mu g) was administered subcutaneously in the clinic setting with single serum luteinizing hormone (LH) measured 40 minutes after injection. A standard IV GnRH stimulation test was performed within 2 weeks, with serum LH obtained at 0, 20, 40, and 60 minutes. LH was assayed by immunochemiluminometric assay. Results. The mean peak LH levels after IV and SQ testing were identical. A significant correlation (r = .88) was found between the LH determined by SQ stimulation and the peak LH determined by IV GnRH testing. CPP was diagnosed (LH, greater than or equal to 8 IU/L) by both SQ and IV testing in 7 of 22 patients and was excluded by both tests in 14 of 22 patients. A diagnostic discrepancy between peak IV and SQ results was seen in 1 patient. Conclusions. We conclude that mean GnRH-stimulated LH levels from rapid SQ and standard IV testing are indistinguishable and that individual LH levels by each method are strongly correlated. A rapid SQ GnRH test is a valid tool for laboratory confirmation of CPP.