Table 15

 Biochemical evidence: positive effect of oral contraceptives on bone metabolism

Study designReferenceNo of patientsOC exposureMeasurement of bone metabolismResults
OC, Oral contraceptive; RCT, randomised controlled trial; EE, ethinyl oestradiol; NTx, N-telopeptides; D-PYR, deoxypyridinoline; BSAP, bone specific alkaline phosphatase; PYR, pyridinoline; Cr, creatinine.
RCT (level 1b)Grinspoon et al9145 women with hypothalamic amenorrhoea (ages 18–40)OC group (35 μg EE+0.18 mg norgestimate, days 1–7; 35 μg EE+0.215 mg norgestimate, days 8–14; 35 μg EE+0.25 mg norgestimate, days 15–21) (n = 25) v placebo (n = 20) for 3 monthsNTx, D-PYRDecrease in NTx and D-PYR in OC treated group (therefore decreased resorption)
Healthy premenopausal
RCT (level 1b)Pinter et al9341 women (ages 20–27)30 μg EE+150 μg levonorgestrel (n = 21) v control (n = 20) for 3 monthsSerum BSAP and osteocalcin, urinary D-PYROC treated: BB genotype, decrease in osteocalcin; in Bb genotype, decrease in BSAP and osteocalcin; bb genotype, no change. Control: no changes in any genotype
Cohort (level 2b)Paoletti et al9430 women (ages 22–30)20 μg EE+75 μg gestodene (n = 10) v 30 μg EE+75 μg gestodene (n = 10) v control (n = 10) for 12 monthsUrinary PYR, D-PYRDecrease in PYR, D-PYR in OC-treated groups (suggesting decreased resorption)
Kitai et al9530 women (mean age 23.7 years)OC users v non-usersUrinary Ca2+/Cr ratioDecrease in Ca2+/Cr with OC use (suggesting decreased resorption); effect more pronounced in non-smokers