The hormones behind hair loss in women

A balance problem more than a single culprit

It is tempting to look for one hormone that has gone wrong. In practice, hair growth reflects a balance: estrogen tends to keep hairs in their growth phase longer, while androgens such as testosterone and DHT can shorten that phase in follicles that are genetically sensitive to them.

The American Academy of Dermatology describes female pattern hair loss as hereditary and notes that it becomes more common after menopause, which suggests hormones play a supporting role. Two women can have identical blood levels and very different hair, because follicle sensitivity is inherited.

Estrogen: what happens as it declines

During the reproductive years, estrogen appears to lengthen the anagen, or growth, phase. As levels fall through perimenopause and menopause, more hairs may cycle out sooner and regrow finer. This is part of why the part line can widen in your late 40s and 50s even when nothing else has changed.

The drop in estrogen also means androgens are less counterbalanced. Androgen levels themselves usually drift down slowly with age rather than rising, so it is the ratio that shifts, not a surge in testosterone.

Androgens and DHT

Inside the follicle, the enzyme 5-alpha reductase converts testosterone into dihydrotestosterone (DHT), a more potent androgen. In susceptible follicles, DHT gradually shrinks hairs over years, a process called miniaturization. StatPearls notes that affected scalp areas show more 5-alpha reductase activity and more androgen receptors.

Testing DHT in the blood rarely helps, because what matters is how the follicle responds locally, not the circulating level. Total and free testosterone are more useful when there are other signs of androgen excess.

SHBG changes how testosterone results read

Sex hormone–binding globulin holds testosterone in the blood so it cannot act on tissues. When SHBG is low, which often happens with insulin resistance or higher body weight, more testosterone is free and active even if total testosterone looks normal. That is why clinicians often order SHBG along with testosterone rather than reading total testosterone alone.

Thyroid and prolactin

Both an underactive and an overactive thyroid can cause diffuse shedding, and thyroid disease becomes more common in women through midlife. MedlinePlus lists thyroid disease among the causes of hair loss and recommends seeing a clinician if hair loss comes with weight gain, cold intolerance, muscle weakness or fatigue.

Prolactin is a pituitary hormone. It is worth checking if you also have irregular or absent periods that are not explained by perimenopause, or nipple discharge when you are not breastfeeding.

Patterns that point somewhere specific

Certain combinations change what a clinician looks for first.

• Thinning plus irregular cycles, acne and new facial hair: suggests androgen excess, such as polycystic ovary syndrome, and calls for an androgen workup.
• Rapid hair loss with a deepening voice or other masculinizing changes: needs prompt in-person assessment to rule out a hormone-producing tumor.
• Sudden diffuse shedding a few months after illness, surgery, stress or fast weight loss: points to telogen effluvium rather than a hormone imbalance.
• Patchy bald spots, scalp redness, scaling or pain: suggests an inflammatory or scarring condition that a dermatologist should see.

Questions worth bringing to your visit

A good history often narrows things faster than a long lab list. Before your appointment, it helps to note when you first noticed the change, whether it was sudden or gradual, what your cycles have been doing, any new medicines or supplements, recent illness or weight change, and whether close relatives on either side of your family had thinning. Photos from a few years ago can also show whether density has really changed or whether it is mostly texture.

A sensible testing plan

A focused panel usually answers the important questions without chasing every hormone. StatPearls recommends thyroid studies, a complete blood count and iron studies including ferritin as part of evaluating androgenetic alopecia.

• Thyroid function (TSH, with free T4 if needed)
• Ferritin and a complete blood count
• Total testosterone and SHBG when androgen excess is suspected
• Prolactin if cycles are irregular or there is nipple discharge
• Estradiol and FSH only when menopausal status is genuinely unclear

What a normal panel means

If your labs come back normal, that is the expected result for ordinary female pattern hair loss, not a sign that something was missed. It means the follicles' inherited sensitivity is the main driver, and treatment such as topical minoxidil, which the AAD lists as an FDA-approved option for women, becomes the focus. Starting early tends to give the best results.

Through HealifyMD, a licensed clinician can review your history, order the Comprehensive Lab Panel ($199, confirmed at eligibility review), and discuss whether a prescription hair treatment fits you. The 4-in-1 hair treatment is compounded, which means it is not FDA-approved.