Urinary N-telopeptides to monitor bone resorption while on GnRH agonist therapy

OBJECTIVES: To assess the utility of urinary cross-linked N-telopeptides in monitoring bone resorption and predicting bone loss during GnRH agonist administration. METHODS: Ninety patients who were prescribed GnRH agonist therapy for 3-6 months for treatment of endometriosis, leiomyomas or other gynecologic disorders participated in this prospective multicenter study. N-telopeptides, serum estradiol (E2), and bone mineral density were monitored before, during and up to 3 months after the course of GnRH agonist therapy. RESULTS: N-telopeptide levels increased significantly throughout GnRH agonist therapy and returned to baseline levels by 3 months after treatment was completed. A significant negative correlation was seen between N-telopeptide and E2 measurements after 3 months (r=-0.23, P<.05), 4 months (r=-0.32, P < .05), and 5 months (r=-0.41, P<.005) of GnRH agonist therapy. The percent change in bone mineral density at L1-L4 at 6 months of GnRH agonist treatment correlated inversely with the percent change in N-telopeptides from baseline to 2,3,4, and 5 months of treatment; the percent change of bone mineral density at the femoral neck at 6 months correlated inversely with the percent change of N-telopeptides from baseline to month 4. CONCLUSIONS: Urinary N-telopeptide determinations provide a quantitative measure of bone resorption, due to GnRH agonist-induced hypoestrogenism. Increases in resorption as measured by N-telopeptides parallel decreases in in E2 levels. Increases in N-telopeptides on GnRH agonist therapy may provide a tool to predict decreases in bone mineral density.

This article has been cited by other articles:

				I. Gorai, Y. Taguchi, O. Chaki, R. K. M. Nakayama, B. C. Yang, S. Yokota, and H. Minaguchi Serum Soluble Interleukin-6 Receptor and Biochemical Markers of Bone Metabolism Show Significant Variations During the Menstrual Cycle J. Clin. Endocrinol. Metab., February 1, 1998; 83(2): 326 - 332. [Abstract] [Full Text]

				E. A. Amama, M. Taga, and H. Minaguchi The Effect of Gonadotropin-Releasing Hormone Agonist on Type I Collagen C-Telopeptide and N-Telopeptide: the Predictive Value of Biochemical Markers of Bone Turnover J. Clin. Endocrinol. Metab., February 1, 1998; 83(2): 333 - 338. [Abstract] [Full Text]

				J. D. Clemens, M. V. Herrick, F. R. Singer, and D. R. Eyre Evidence that serum NTx (collagen-type I N-telopeptides) can act as an immunochemical marker of bone resorption Clin. Chem., November 1, 1997; 43(11): 2058 - 2063. [Abstract] [Full Text] [PDF]