Underarm Hair Changes: Hormones in 2026

You’ve probably noticed your underarm hair changing over the years, maybe getting coarser or growing faster. Most people just blame age or their lifestyle, but the real story is hormones. The density and coarseness of your underarm hair are almost entirely dictated by hormonal shifts throughout your life, and understanding what’s going on inside explains exactly why that hair might suddenly feel different.

The Role of Androgens in Hair Growth

Androgens are steroid hormones mainly associated with male traits, but they’re present and working in both sexes. When we’re talking about hair growth, the two that matter most are testosterone and its much more potent form, dihydrotestosterone (DHT). Your underarm hair follicles are loaded with androgen receptors, and when these hormones lock on, it’s like a switch gets flipped, telling the follicle to produce what’s known as terminal hair, the thick, coarse, pigmented stuff.

This is exactly why your underarm and pubic hair is so much coarser than the fine, vellus “peach fuzz” on your arms. How much coarse hair you actually get depends on your follicles’ sensitivity to androgens, which is mostly down to your genes. The body’s *response* to the hormones, not just the raw amount of them in your system, is what really determines your personal hair density and texture.

We have solid science on this. A 2021 study published in the Journal of the American Academy of Dermatology, for example, found a direct link between androgen receptor gene expression and the actual diameter and growth cycle of hair shafts in these sensitive areas. This research confirms that these hormones are the primary architects building coarse underarm hair.

Puberty: The Initial Hormonal Surge

The first, and most dramatic, time you see coarse underarm hair is during puberty. As the body shifts into this stage, it starts cranking out way more sex hormones, including androgens. In boys, the testes ramp up testosterone production. In girls, the ovaries and adrenal glands start producing a smaller but very meaningful amount of androgens alongside estrogen.

This androgen flood is what triggers the fine vellus hair in the armpits to transform into that dark, thick, noticeable terminal hair. When and how much this happens varies a ton from person to person depending on their genetics, nutrition, and general health. For most, it’s a clear biological marker of sexual maturation and the first time they ever have to think about hair removal.

It’s worth remembering that while everyone goes through puberty, the results aren’t uniform. Is there a “normal” amount of underarm hair? Not really. Some people end up with very dense, coarse patches, while others have much sparser growth. This huge variability just shows how complex the interaction between genes and individual hormone sensitivity really is.

Hormonal Shifts Beyond Puberty: Pregnancy and Menopause

Hormonal changes don’t just stop after your teen years. They keep going, especially for women, and two of the biggest hormonal rollercoasters, pregnancy and menopause, can definitely change your underarm hair.

Pregnancy-Related Hair Changes

During pregnancy, a woman’s body is a wild cocktail of hormones. While estrogen and progesterone are through the roof, androgen production can also tick up, particularly in the second and third trimesters. This is why many pregnant clients say their hair (underarm, belly, face) is suddenly growing faster and seems thicker. This is almost always a temporary thing. After the baby is born and hormones start to settle, there’s usually a shedding phase where hair density goes back to its pre-pregnancy state.

Menopause and Androgenic Effects

Menopause signals the end of a woman’s reproductive cycle, and it’s defined by a steep drop in estrogen. While estrogen plummets, androgen levels (mostly testosterone) tend to stay more stable or decrease much more slowly. This creates a new balance where the influence of androgens is relatively stronger. For some women, this means thinning hair on their head, but paradoxically, it can fire up new or more coarse hair growth on the upper lip, chin, and underarms. I see this constantly with clients in their late 40s and 50s. They’re often shocked that their armpit hair is suddenly more stubborn and dense, even as other body hair might be thinning out.

A 2023 review in Climacteric: The Journal of the International Menopause Society went into detail about how the hormonal shifts of perimenopause and menopause affect skin and hair. The authors specifically pointed out that hirsutism (excessive coarse hair) becomes more common in women because the altered androgen-to-estrogen ratio directly affects what the follicles do.

Medical Conditions and Hormonal Imbalance

Sometimes, changes in underarm hair aren’t just about life stages, they can signal an underlying medical condition. Figuring out these root causes is the only way to effectively manage the hair growth.

Polycystic Ovary Syndrome (PCOS)

Polycystic Ovary Syndrome (PCOS) is a very common endocrine disorder in women of reproductive age. One of its defining traits is hyperandrogenism, or having way too high androgen levels. This hormonal imbalance shows up as irregular periods, acne, and hirsutism, which is the growth of coarse, dark hair in a male-like pattern (upper lip, chin, chest, back, and definitely the underarms). The extra androgen stimulation makes the follicles in those areas produce more strong hair growth. Managing PCOS usually involves a doctor-led plan with lifestyle changes and medication to regulate hormones.

Adrenal Gland Disorders

Your adrenal glands, which sit on top of your kidneys, make a variety of hormones, including some androgens. Problems like adrenal hyperplasia (where the glands get too big) or certain adrenal tumors can cause them to pump out way too many androgens. This can lead to virilization, with symptoms like a deeper voice, more muscle mass, and a lot of new, coarse body hair, including in the armpits. These conditions are much rarer than PCOS but are another example of how messed-up hormones can radically change hair patterns.

Thyroid Dysfunction

This one isn’t a direct androgen problem, but your thyroid hormones are critical for your metabolism and the health of your hair follicles. Both an underactive thyroid (hypothyroidism) and an overactive one (hyperthyroidism) can throw a wrench in hair growth. Hypothyroidism, for example, can make hair brittle and coarse, though its direct effect on underarm density isn’t as clear as it is for androgen conditions. Hyperthyroidism can make hair finer and more likely to fall out. So while thyroid issues don’t directly cause coarse armpit hair, they can definitely complicate the picture and make it hard to know what’s really going on.

If you see a sudden, major change in your underarm hair, especially if it comes with other symptoms like weird periods, weight changes you can’t explain, or new skin problems, it’s always a good idea to see a doctor. They can run tests to figure out if there’s a hormonal imbalance or another medical issue at play.

Managing Coarse Underarm Hair Influenced by Hormones

So, you know hormones are the cause. What can you actually do about it? You can’t just flip a switch on your hormones without a doctor’s help, but you have a lot of control over the hair itself.

For hair that’s gotten coarser or denser from hormonal shifts, professional hair removal methods are often the most practical solution. These techniques get the hair at the follicle, giving you smoother skin for way longer than just shaving. Consistent removal (like waxing or sugaring) can also, over time, make the regrowth appear finer and less dense, even if the hormones are still doing their thing. And let’s clear this up: removing hair does not make it grow back thicker. That’s a myth. The perception of thickness comes from the blunt, stubbly tip of a shaved hair, which feels much coarser than a hair with its natural, tapered end.

If a doctor identifies a condition like PCOS as the culprit, they might suggest specific treatments. This could be hormonal birth control to regulate androgen levels or even anti-androgen medications to get at the root cause. When the underlying hormonal problem is managed, you’ll often see the unwanted hair growth slow down. The best results usually come from tackling it from both ends: medical treatment for the hormones and effective hair removal for the hair that’s already there.

Of course, lifestyle choices have a supporting part. A balanced diet, keeping stress in check, and getting enough sleep all contribute to better hormonal health, though their direct effect on underarm hair might be pretty subtle. Really, the smartest path is a mix of understanding your own body, talking with professionals (both medical and aesthetic), and finding a hair removal routine that you’re comfortable with.

It’s clear that the texture and amount of your coarse underarm hair are tied directly to hormonal activity, particularly androgens. From the huge changes during puberty to the fluctuations during pregnancy and menopause, and even the effects of conditions like PCOS, hormones are running the show. Knowing this gives you the power to make better choices about how you manage your body hair and tells you when it might be time to check in with a doctor.