La. Marshall et al., URINARY N-TELOPEPTIDES TO MONITOR BONE-RESORPTION WHILE ON GNRH AGONIST THERAPY, Obstetrics and gynecology, 87(3), 1996, pp. 350-354
Objective: To assess the utility of urinary cross-linked N-telopeptide
s in monitoring bone resorption and predicting bone loss during GnRH a
gonist administration. Methods: Ninety patients who were prescribed Gn
RH agonist therapy for 3-6 months for treatment of endometriosis, leio
myomas, or other gynecologic disorders participated in this prospectiv
e multicenter study. N-telopeptides, serum estradiol (E2), and bone mi
neral density were monitored before, during, and up to 3 months after
the course of GnRH agonist therapy. Results: N-telopeptide levels incr
eased significantly throughout GnRH agonist therapy and returned to ba
seline levels by 3 months after treatment was completed. A significant
negative correlation was seen between N-telopeptide and E2 measuremen
ts 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 perce
nt change in bone mineral density at L1-L4 at 6 months of GnRH agonist
treatment correlated inversely with the percent change in N-telopepti
des from baseline to 2, 3, 4, and 5 months of treatment; the percent c
hange in bone mineral density at the femoral neck at 6 months correlat
ed inversely with the percent change of N-telopeptides from baseline t
o 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 E2 levels. Increases in N-telopeptides on GnRH
agonist therapy may provide a tool to predict decreases in bone minera
l density.