Does Yaz Cause Bone Density Loss?
No, Yaz (drospirenone 3 mg/ethinyl estradiol 20 µg) does not cause bone density loss in healthy reproductive-age women without osteoporosis risk factors; in fact, it maintains bone mass and reduces bone turnover markers.
Evidence in Healthy Reproductive-Age Women
The available evidence specifically examining Yaz and similar drospirenone-containing formulations demonstrates bone-protective effects:
A 12-month randomized controlled trial comparing 20 µg ethinyl estradiol plus 3 mg drospirenone (Yaz formulation) showed no significant difference in spinal bone mineral density compared to baseline or controls 1
Both 20 µg and 30 µg ethinyl estradiol formulations with drospirenone significantly reduced bone resorption markers (urinary pyridinoline and deoxypyridinoline) at 6,9, and 12 months, indicating decreased bone breakdown 1
A 6-month study of drospirenone/ethinyl estradiol demonstrated decreased bone turnover with unchanged bone mineral density at the heel, suggesting bone preservation 2
Mechanism of Bone Protection
Combined oral contraceptives containing adequate estrogen doses maintain bone health through:
Suppression of bone resorption markers while maintaining bone formation, creating a favorable bone balance 1, 2
Provision of exogenous estrogen that prevents the accelerated bone loss seen with estrogen deficiency 3
Important Clinical Context and Caveats
When COCs May NOT Protect Bone:
The most critical caveat: Combined oral contraceptives may impair peak bone mass acquisition if started within the first 3 years after menarche in adolescent girls 4. This is a distinct population from healthy reproductive-age women.
In women with functional hypothalamic amenorrhea (FHA), combined oral contraceptives are inferior to transdermal estradiol for bone protection because COCs inhibit IGF-1 production via first-pass hepatic metabolism, reducing osteoblastic activity 5. However, this applies to a specific pathological condition, not healthy women.
Comparison to Other Estrogen Formulations:
Transdermal 17β-estradiol with progesterone demonstrates superior bone mineral density effects compared to oral ethinyl estradiol in certain populations (premature ovarian insufficiency, functional hypothalamic amenorrhea) 5
The Endocrine Society guidelines favor transdermal estradiol over combined oral contraceptives specifically for treating bone loss in functional hypothalamic amenorrhea, not for routine contraception in healthy women 5
Clinical Bottom Line for Your Patient
For a healthy reproductive-age woman without osteoporosis risk factors using Yaz for contraception, bone density loss is not a concern. The formulation maintains bone mass and reduces bone turnover markers 1, 2.
Do not confuse this with:
- Adolescents in early post-menarche years (where COCs may impair peak bone mass) 4
- Women with functional hypothalamic amenorrhea or premature ovarian insufficiency (where transdermal estradiol is preferred) 5
- Postmenopausal women (where HRT has different risk-benefit considerations) 6, 3
In adult women using COCs throughout reproductive years, studies report neutral or beneficial effects on bone health, with no association between COC use and fracture risk 4.