Does spironolactone affect bone density?

Short answer: the studies in this archive do not show spironolactone lowering bone density. In one trial it appeared to protect bone density in a situation where bone loss would otherwise be expected, and in another it made no difference either way when combined with the contraceptive pill. There is no study here showing spironolactone causing bone loss on its own.

What the direct evidence shows

One controlled trial looked at this question head-on, though not in a straightforward setting. It followed 41 women with polycystic ovary syndrome (PCOS) who were given a GnRH agonist, a drug that suppresses ovarian hormone production and is known to reduce bone mineral density as a side effect. Some of these women received the GnRH agonist alone, some with spironolactone added, and some with a different antiandrogen, flutamide, added. After six months, bone mineral density had dropped at the spine, femoral neck, and Ward's triangle in the women on the GnRH agonist alone and in those on the GnRH agonist plus flutamide. The group given the GnRH agonist plus spironolactone showed no such drop — their bone density stayed close to baseline (controlled trial, 1999). The study did not establish why this happened; the authors described the mechanism as still unclear.

A second trial looked at spironolactone in a more common real-world combination: alongside the contraceptive pill. Twenty-two women with hyperandrogenism took an oestrogen-progestin pill alone, and twenty-one took the same pill plus spironolactone, for twelve months. Bone mineral density was measured before and after. There was no meaningful difference between the two groups, and no significant change in bone turnover markers either. The authors concluded that adding spironolactone to this pill regimen at the doses used did not affect bone density one way or the other, while still improving hirsutism symptoms (controlled trial, 2001).

What this does and doesn't tell us

Taken together, these two studies point away from spironolactone causing bone loss. In the first, it appeared to prevent the bone loss that another antiandrogen (flutamide) did not prevent, under conditions of hormone suppression. In the second, it made no measurable difference to bone density when added to a standard contraceptive regimen. Neither study, though, tested spironolactone as a single agent in women who were not also on a GnRH agonist or the pill, over a longer stretch of time. The archive doesn't contain a large-scale or long-term study of spironolactone's effect on bone density used alone, so what happens over years, or in women past menopause who aren't on hormonal contraception, remains unanswered here.

How this fits with what spironolactone is used for

These bone studies were both done in women being treated for androgen-related symptoms — hirsutism and PCOS-related hormone patterns — which is the same population covered elsewhere in this archive. If you're weighing up spironolactone for excess hair growth, the page on whether spironolactone helps with excess facial or body hair covers the evidence on that specific effect, and the question of using it for months or years is addressed separately on is spironolactone safe to take long term for excess hair. Neither of the bone studies here reports on how long women could reasonably expect to stay on the drug, so that long-term safety question and the bone density question, while related, aren't the same evidence.

It's also worth noting that both bone studies involved spironolactone combined with something else — a GnRH agonist in one case, the contraceptive pill in the other — rather than spironolactone taken by itself with no other hormonal treatment. Combining spironolactone with the pill is itself a common approach for excess hair, and the archive has a separate look at whether that combination works better than spironolactone alone, on the page about birth control pills plus spironolactone. Readers interested in how spironolactone compares with other options for PCOS symptoms more broadly may also want the page on spironolactone versus metformin for PCOS.

What's still unknown

The two studies here answer a fairly narrow question: what happens to bone density over about six to twelve months when spironolactone is added to a GnRH agonist or to the contraceptive pill, in women with PCOS or hyperandrogenism. Neither study followed women for years, neither included women past menopause, and neither tested spironolactone given entirely on its own without another hormonal drug alongside it. The proposed bone-protective mechanism in the GnRH agonist study was flagged by the authors themselves as unexplained. So while nothing in this archive points to spironolactone harming bone density, the evidence is limited to these two specific settings, and a broader, longer-term picture isn't available here. For a related but distinct safety question — whether spironolactone use is linked to cancer risk — there is a separate page: is spironolactone linked to a higher risk of cancer. General background on hair-related conditions and their treatments can also be found in the hair and nails archive.