Correlation of estradiol, parathyroid hormone, interleukin-6, and soluble interleukin-6 receptor during the normal menstrual cycle

Rodent models suggest that estradiol deficiency promotes bone loss through increasing interleukin-6 (IL-6) activity. However, it is controversial as t o whether these findings are applicable to humans. To evaluate estradiol-me diated modulation of IL-6 activity in relation to bone metabolism in humans , we measured serum IL-6, soluble interleukin-6. receptor (sIL-6R), estradi ol (E-2), progesterone, luteinizing hormone, follicle-stimulating hormone, intact parathyroid hormone (PTH), serum and urine Ca, and bone biochemical markers (serum bone-specific alkaline phosphatase, osteocalcin, and serum a nd urine deoxypyridinoline [Dpd]) across one menstrual cycle for 20 women. Neither IL-6 nor sIL-6R levels differed between the follicular phase (FP) a nd the luteal phases (LP). However, IL-6 was negatively correlated with E-2 during the FP (p = 0.003), Furthermore, IL-6 correlated positively with se rum Ca over the entire cycle (p = 0.009), Serum Ca correlated positively wi th serum (p = 0.040) and urine (p = 0.006) Dpd, PTH was significantly highe r during the FP than in the LP (p = 0.004). PTH was negatively related to E -2 (p = 11,002), serum Ca (p < 0.001), and urine Ca (p = 0.036), whereas it was positively correlated with IL-6 (p = 0.027), These data demonstrate th at IL-6 and PTH fluctuate with E-2, and serum IL-6 is associated with PTH l evels during the menstrual cycle. However, the role of IL-6 in bone remodel ing during the normal menstrual cycle remains to be determined. (C) 2000 by Elsevier Science Inc. All rights reserved.