Which hormones cause hair loss? Understanding the hormonal links behind thinning hair

To say that our hormones take us on a rollercoaster throughout our lifetimes would be quite the understatement. From puberty through to menopause and beyond, the complex interplay of oestrogen, progesterone and androgens touches nearly every aspect of our lives.

But — given it's much more subtle than that luteal phase breakdown or pre-menstrual acne — one area where we don't often consider hormonal influences is our hair. And yet, for both men and women, what's going on in our reproductive systems directly influences what's on our heads.

If you've been experiencing hair thinning or loss — or your locks are just looking a bit more lacklustre than usual — it's possible that hormonal factors could be to blame. The good news is, by identifying hormonal triggers, you can take a targeted approach to promote hair growth and get back to feeling like yourself again.

But which hormones cause hair loss in females, exactly? And, how can you tell hormone-triggered shedding apart from other hair loss conditions? Read on for everything you need to know about the link between hormones and female hair loss.

What causes hair loss?

It's important to note that some hair loss and thinning is a normal part of ageing. Over time, our hair follicles naturally shrink, producing finer, thinner, or fewer strands. Just like skin ageing, most women start to notice this process gradually in their thirties and forties — speeding up in their fifties and beyond. By the age of seventy, over half of women are expected to notice some hair loss [1]. So, if you don't have the same fullness or vibrance you had in your twenties, that's not necessarily cause for concern.

However, if you notice significant thinning or loss in a short amount of time, it could be a sign that other factors are at play — and not all of them are hormone-related. Some other common causes of hair loss include [2]:

• Rapid weight loss
• Extreme stress, which can be chronic (long-term) or acute (a reaction to traumatic events)
• A side effect from medications (such as for arthritis, depression, heart issues, and high blood pressure), chemotherapy and radiation
• The result of illness, such as diabetes or autoimmune disorders
• Hair styling and care, such as excessive use of heated hair tools or tight hairstyles (known as traction alopecia)
• Vitamin or nutrient deficiencies, such as vitamin C, vitamin D or zinc

Understanding hair growth cycles

At any given time, each of our hair follicles is somewhere in a natural cycle of rest and rejuvenation. This process has four overlapping stages, each with its own unique role [3]:

Anagen (growth phase)

This is the active, growing phase wherein cells divide rapidly in the hair follicle root. This stage can last between 2 and 7 years, with hair growing about 1 cm every 28 days. At any given time, 80 to 90% of our hair is in this stage.

Catagen (transition phase)

Lasting roughly 2 to 3 weeks, this short transition phase sees the follicle detach from the dermal papilla (blood supply), shrink and stop growing

Telogen (resting phase)

This is the resting period where the follicle remains inactive while the hair is held in place. Lasting about 3 months, roughly 10 to 15% of our scalp hairs are in this stage.

Exogen (shedding phase)

Sometimes considered part of the telogen phase or as its own separate final stage, this is when the old hair is released and falls out. It's normal to lose 50 to 100 hairs per day in this shedding process.

The stages of the hair cycle

At the root (pun intended) of most hair loss is telogen effluvium: a name for temporary, excessive shedding caused by shock to the body [4]. When the body is under stress, it produces cortisol, causing the hair follicles to enter the telogen phase prematurely. When this happens, we can lose around 300 hair follicles per day [5]. As you can imagine, this can significantly impact hair fullness.

How hormones influence hair growth and shedding

The relationship between hormones and hair loss (and growth) is more direct than you might think. Much like a traffic light system, our hormones signal to our hair follicles when it's time to grow, rest or shed. When there's an imbalance affecting one or more of your hormones, it can shorten, prolong or cause premature entry to any of the hair growth cycles. This, in turn, can lead to hair shedding or increased growth in less desirable areas,  such as the chin, upper lip, chest, back, arms or abdomen.

Hormones that can affect hair loss

Further contributing to the complexity, each of our reproductive hormones plays a different role in this start/stop hair growth cycle.

Oestrogen

As well as playing a crucial role in female development and regulating the menstrual cycle, oestrogen (or estrogen) is also directly involved in hair growth. The higher our oestrogen levels, the longer our hair follicles tend to stay in the anagen (growth) phase. This is part of the reason women tend to have greater natural hair density during the reproductive years [6].

On the flipside, as oestrogen declines, it causes healthy hair follicles to enter the telogen (resting) phase sooner. This means that the hair spends less time growing and more time resting and shedding [7].

Androgens

Oestrogen also plays a protective role against androgens — male sex hormones that females also possess in small amounts. These hormones, such as DHEAS, DHEA, DHT and testosterone, play an important role in the female body. They assist with reproductive function, libido, bone and muscle mass retention, as well as cognition and motivation [8].

However, an excess of these hormones can trigger androgenetic alopecia by shortening the anagen (growth) phase [7]. It can also accelerate a process called miniaturisation, where the follicles convert from thick 'terminal' hairs to thin 'vellus' hairs (which are more susceptible to shedding).

Interestingly, an excess of the hormone DHT (which men naturally have more of than women) is the biggest cause of male pattern baldness. This is why baldness is more common in men overall than women [9]. While it is possible for women to experience male pattern baldness due to androgenetic alopecia, this is much rarer.

In women, hair loss related to DHT levels or other androgens is called female pattern hair loss or female pattern baldness [10].  While men tend to see a receding hairline, a widening of the centre part and diffuse thinning at the crown is much more common in women.

Progesterone

The other key female hormone involved in the menstruation and reproduction dance, progesterone, helps to prepare the lining of the uterus for embryo implantation. It's also a hair-helping hormone, as it helps block DHT and other testosterones from disrupting the hair growth cycle.

However, when progesterone drops — whether that's due to stress, perimenopause or menopause — the relative influence of testosterone is higher [7]. Low progesterone levels can also trigger the production of the stress hormone, cortisol, which can further exacerbate hair loss in women [11].

Thyroid hormones

Our thyroid hormones play a regulating role in nearly every system in the body, for both men and women. The hair growth cycle is no exception, with both triiodothyronine (T3) and thyroxine (T4) modulating the growth (anagen) phase. When balanced, they also help to stimulate keratinocytes: matrix cells that support increased hair growth. However, the opposite is also true, and hair loss can be a sign of thyroid issues.

Common hormonal conditions linked to hair loss

There are several hormonal conditions that can cause changes to our hair, including:

PCOS

Polycystic ovary syndrome, or PCOS, is a common (yet often debilitating) hormonal disorder caused by an imbalance of androgens. As well as irregular or painful periods, acne and difficulties with conceiving, many women with PCOS experience hair loss and thinning [12]. This happens because the elevated male hormones (particularly DHT) bind to the hair follicles, causing them to shrink and become inactive. PCOS also tends to be accompanied by lower oestrogen and progesterone levels, which can also contribute to androgenetic alopecia.

Insulin resistance

While technically a metabolic condition, not a hormonal one, roughly 70% of women with PCOS also have insulin resistance [13]. This is when the body's cells stop responding effectively to insulin, a hormone that regulates blood sugar. As well as creating challenges for weight maintenance and increasing the risk of type 2 diabetes, it can also contribute to hair thinning. This is because insulin resistance decreases Sex Hormone-Binding Globulin (SHBG), leaving more free testosterone to damage hair follicles [14].

Thyroid disorders

When our thyroid hormones are out of whack, it can cause hair loss in two different ways [15]. Hyperthyroidism (excessive production of T3 and/or T4) can cause hair to become fine, soft, and thin, with accelerated, premature shedding. Meanwhile, hypothyroidism (underactive thyroid hormones) can lead to sparse, brittle, dry, and slow-growing hair due to an extended resting (telogen) phase.

Menopause and perimenopause

Perimenopause (the 4-10 year lead-up to menopause) and menopause (the permanent end to menstruation) are natural life transitions, not hormonal conditions. However, for some women, the symptoms can hit like a ton of bricks, especially if they enter these stages early. As perimenopause and menopause transitions are accompanied by a steep drop in oestrogen and progesterone, hair loss and thinning are common, especially around the crown. Thankfully, the growing availability of Hormone Replacement Therapy (HRT) makes it easier to manage the symptoms, including menopausal hair loss.

How hormonal hair loss is diagnosed

To determine whether your hair loss is hormonal or caused by other factors, your doctor won't just examine your hair. Instead, they'll look at the whole picture: your life stage, lifestyle, family history, overall health and stressors. Your doctor may use a physical scalp exam, hormonal blood tests and a scalp biopsy or trichoscopy to help diagnose hormonal hair loss. They'll also likely consider whether your presentation is consistent with the typical female pattern hair loss seen in androgenetic alopecia.

In some cases, your doctor may refer you to a specialist like a dermatologist, trichologist, or endocrinologist for a second opinion.

What treatments can help with hormonal hair loss?

As noted, hormonal replacement therapy (HRT) can be a game-changer for women experiencing menopausal hair loss.  Meanwhile, for those with PCOS or other hormonal imbalances, spironolactone is an anti-androgen medication often used in women to block androgens that cause follicular miniaturisation (and thus, prevent hair falling).

However, these hormonal hair loss treatments can have significant side effects and won't be suitable for everyone. For women with early-stage or temporary (such as due to pregnancy) hair loss, topical solutions such as Boost by Juniper can go a long way. This gentle, non-irritating serum contains antioxidants and antimicrobial oils for optimal scalp health. This can also be paired with Regrow by Juniper: a chewable oral medication that takes a targeted approach to support hair growth while preventing further hair loss.

For women in the more advanced stages of hormonal hair loss, Restore by Juniper is a dual-action oral medication that features two active ingredients that reduce hormone-driven shedding over time. With a chewable or sublingual (under the tongue) formula, it's convenient enough to take every day. You can also access the tried-and-tested Regaine through Juniper. Clinically proven to regrow hair, the topical minoxidil foam delivers visible results in as little as 3 to 6 months.

Of course, it's one thing to start using a hormonal hair loss product. It's another thing entirely to use it consistently and stay the course — especially when results aren't immediate. That's where Juniper's Hair Renewal Treatment system comes in. As well as access to a personal, science-based haircare treatment, you also get access to automatic and discreet delivery and unlimited consults and support whenever you need it.

When to speak to a healthcare professional

As hair is such a portal into our overall health, losing locks can be a sign that something is awry in your body. If you've lost a noticeable amount of hair in a short amount of time or notice it falling out in clumps, it's important to see a doctor so they can rule out anything serious. The same goes for if your hair loss is accompanied by other mysterious symptoms like sudden hair loss, fatigue and aches or pains.

Already ruled out alternate causes and just want to get your self-esteem back on track? With Juniper, your hair health journey starts with a free initial consult with a clinician who is an expert in weight and hormone-driven hair loss. In tandem with your GP, they'll be able to help you get to the bottom of what's going on and recommend treatment options based on your unique situation.

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