Hair loss is not a commonly reported side effect of Tymlos (abaloparatide). It does not appear in the drug’s prescribing information as a known adverse reaction from clinical trials. However, some patients have reported hair thinning or shedding while taking Tymlos, which raises a fair question about whether the drug plays a role or something else is going on.
What Clinical Trials Show
During the clinical trials that led to Tymlos’s FDA approval, hair loss was not identified as a side effect at a rate higher than what occurred in patients taking a placebo. The most commonly reported side effects were nausea, dizziness, headache, heart palpitations, fatigue, upper abdominal pain, and vertigo. Redness at the injection site was also frequent. Hair loss simply didn’t show up as a pattern in the trial data.
That said, clinical trials track side effects over a limited time and in a specific population. Rare or slower-developing effects sometimes only become apparent once a drug reaches a much larger group of patients in real-world use. Individual reports of hair changes exist in patient forums and adverse event databases, but these reports alone can’t prove causation because of how many other factors are involved.
How the Drug Interacts With Hair Biology
Tymlos is a synthetic version of a protein related to parathyroid hormone, and this family of proteins does interact with hair follicle cycling. Research in animal models has found that parathyroid hormone-related peptide (PTHrP) stimulates and accelerates the hair cycle. It promotes hair follicles’ transition between growth phases, and in models where hair follicles were damaged or dormant, PTHrP agonists actually promoted hair regrowth, possibly by activating a key growth signaling pathway.
In other words, the biological mechanism of drugs like Tymlos would, if anything, be expected to push hair follicles into active growth rather than cause them to fall out. This doesn’t rule out individual variation or unexpected responses, but the underlying science doesn’t point toward hair loss as a predictable outcome.
Why Hair Loss Happens During Treatment
The typical Tymlos patient is a postmenopausal woman with osteoporosis, and this population is already at elevated risk for hair thinning from several overlapping causes. Sorting out whether the drug or these other factors are responsible can be genuinely difficult.
Menopause itself is a major driver of hair changes. The drop in estrogen levels that defines menopause directly affects hair follicles, leading to thinner, slower-growing hair. As estrogen declines, the relative influence of androgens increases, which can shrink follicles in a pattern similar to what causes male-pattern baldness. This process is gradual, so you might not notice it until it reaches a tipping point, which could coincidentally line up with starting a new medication.
Aging compounds the problem. Blood flow to hair follicles decreases over time, limiting the delivery of nutrients that keep follicles healthy. Hair cycles become shorter, follicles spend more time in resting phases, and the total number of active follicles declines. Researchers have described this as “chronogenetic alopecia,” or age-related hair loss, a condition that predominantly affects women.
Nutritional deficiencies are another common factor in this population. Deficiencies in vitamin D, iron, zinc, and biotin all contribute to hair loss, and women with osteoporosis frequently have suboptimal levels of these nutrients. Stress, other medications (blood pressure drugs, thyroid medications, and antidepressants are common culprits), and underlying health conditions like thyroid disorders can also trigger shedding.
What to Look For
If you’ve noticed increased hair shedding after starting Tymlos, pay attention to the timing. Hair follicles operate on cycles that last several months, so a true drug-related effect would typically appear weeks to months after starting treatment rather than immediately. Shedding that was already progressing before you started Tymlos points more strongly toward hormonal or age-related causes.
Consider whether anything else changed around the same time: a new medication, increased stress, a shift in diet, or a recent illness. Even a high fever or surgery in the months before starting Tymlos could trigger a wave of shedding that shows up later, creating a false association with the new drug.
If hair loss is significant or distressing, your doctor can check for treatable causes like thyroid dysfunction, iron deficiency, or low vitamin D. These are straightforward blood tests and, if a deficiency is found, correcting it often slows or reverses the thinning. Tracking whether hair loss stabilizes, worsens, or improves over the course of your Tymlos treatment can also help distinguish a coincidence from a genuine drug effect.