Comparison of Circadian Variation of Urinary N-terminal Telopeptide of Type I Collagen (NTX) in Healthy Premenopausal Women, Blind Subjects and Permanent Hypoparathyroid Patients

S DI GREGORIO; S.N. ZENI; M.B. OLIVERI,; A WITTICH; C CASCO; J SOMOZA; E CUTRERA; C MAUTALEN; D CARDINALI

POHENIX -ARIZONA -USA

Congreso; XXIII Congreso Anual de la ASBMR; 2001

ASBMR

Presentation Number: M390Diurnal rhythm bone turnover has been reported in several bone metabolic markers; however its etiologyis not known. This study was performed to clarify the influence of PTH or luminous stimulus on thecircadian variation of the bone resorption marker NTX.Six healthy women (aged: 31-45) (G1), six blindsubjects (congenital amaurotic people) (G2) and six hypoparathyroid patients (undetectable PTH)(G3)were recruited for the study. Twenty-four hours urine was collected in six separate samples: between 8and 12 a.m,12 am and 4 p.m, 4 and 8 p.m., 8 and 12 p.m., 0 and 4am, 4 and 8 a.m. NTX was measured byELISA (Osteomark) and expressed as absolute amount in nMECO per 4 h corrected by creatinineexcretion (mM). Results (mean±SE).(*) p<0.0001 compared to G2 and G3. (#) p<0.01 minimalsignificant valueSimilar circadian patterns exhibiting a peak value between 4 and 8am and the lowestvalue between 8am and 4 pm in G2 and between 4 and 8pm in G1 and G3 were observed, althoughconcentration of NTX excretion was significantly higher in healthy women than in hypoparathyroidpatients or blind subjects. These results suggest that hypoparathyroid patients present a diurnal rhythm ofbone resorption that is partly independent of PTH. The rhythm in bone resorption seems to beendogenous, as shown by its persistence in blind people. Conversely, healthy pre-menopausal womenhave higher levels of NTX excretion, because of the PTH-dependent and light-dependent components ofbone resorption. According to these findings the circadian rhythms of NTX excretion seem to berelatively unaffected by PTH and light. However, the magnitude of its response is clearly affected by thetwo factors considered in this abstract.