Female-Pattern Hair Loss: the hormonal panel to Run First

Female-pattern hair loss (FPHL) is the most common form of hair thinning in women, affecting roughly 40% by age 50 (Ramos & Miot, 2015). And yet the standard advice — "try minoxidil, see what happens" — skips a step that changes outcomes: figuring out why the follicles are miniaturizing in the first place.

In women, the answer is almost always hormonal, nutritional, or both. Below is the panel worth having in hand before you commit to a serious protocol.

Why FPHL is a hormonal problem, not just a genetic one

The classic explanation — inherited androgen sensitivity at the follicle — is true, but incomplete. Female follicles are exquisitely responsive to circulating androgens (testosterone, DHT, DHEA-S), thyroid hormone, iron stores, and insulin signaling. Change any of those inputs and the hair cycle changes with it.

That's why two women with identical family histories can have wildly different trajectories. One has normal ferritin and a quiet thyroid; the other is running on ferritin of 18 ng/mL with subclinical hypothyroidism and doesn't know it.

Treating FPHL without checking those inputs is like prescribing statins without a lipid panel. You might get lucky. Usually you don't.

The androgen labs — the ones most clinicians skip

Androgens are the headline actors in FPHL, but "testosterone" alone is a poor readout. A useful androgen workup includes:

• Total testosterone — establishes the baseline, but most bioactive testosterone is bound.
• Free testosterone (calculated or equilibrium dialysis) — the fraction actually reaching the follicle.
• SHBG (sex hormone-binding globulin) — low SHBG unmasks free androgens; often low in insulin resistance and PCOS.
• DHEA-S — adrenal androgen output. Elevated DHEA-S with normal testosterone points upstream, to the adrenal gland.
• Androstenedione — a precursor often elevated in PCOS and late-onset congenital adrenal hyperplasia.
• 17-hydroxyprogesterone — screens for non-classic CAH, which mimics PCOS and is missed constantly.

Why this matters clinically: a woman with normal total testosterone but SHBG of 22 nmol/L and elevated free testosterone has an androgen-driven picture that a total-T-only screen would miss (Carmina et al., 2019). Treatment — whether that's spironolactone, an oral contraceptive, or metformin for the underlying insulin resistance — depends on knowing which lever to pull.

If SHBG is low, assume there's an insulin story underneath. Address it, and the androgens often follow.

Thyroid: the quiet driver everyone underdoses

Hair follicles carry thyroid hormone receptors, and even subclinical hypothyroidism prolongs the telogen (resting) phase and increases shedding (van Beek et al., 2008).

A usable thyroid panel for hair concerns:

• TSH — but interpret tightly. Optimal for hair is generally 0.5–2.5 mIU/L, not the lab-range ceiling of 4.5.
• Free T4 and Free T3 — because central conversion problems get missed on TSH alone.
• Reverse T3 — optional, useful if there's stress or chronic illness in the picture.
• TPO and thyroglobulin antibodies — Hashimoto's is present in a meaningful subset of women with unexplained shedding, and antibody positivity can precede TSH changes by years.

{callout: The clinical takeaway} A TSH "in range" at 3.8 with positive TPO antibodies and diffuse shedding is not a normal thyroid — it's early autoimmune disease, and it changes the treatment order.

Ferritin and iron: the deficiency hiding in plain sight

Ferritin is the single most-cited deficiency in female hair loss workups, and for good reason. Low iron stores impair the matrix cells at the hair bulb, shortening anagen (growth phase).

The target for hair regrowth is not the lab's lower limit. Most dermatology literature suggests ferritin above 40–70 ng/mL to support anagen, with some clinicians pushing toward 70–100 in active shedders (Kantor et al., 2003). A ferritin of 22 is technically "normal" and clinically inadequate for a woman losing hair.

Pair ferritin with a CBC, serum iron, TIBC, and transferrin saturation to distinguish true iron deficiency from inflammatory ferritin suppression — because ferritin is also an acute-phase reactant, and a "normal" 60 in the context of high CRP may actually be low.

The metabolic labs: insulin is a follicle hormone too

Insulin resistance drives SHBG down, free androgens up, and follicle miniaturization forward. It's the mechanism linking PCOS to FPHL, and it's why the metabolic panel belongs on the hair workup:

• Fasting glucose and fasting insulin — calculate HOMA-IR (values above ~2.0 suggest insulin resistance).
• HbA1c — the trailing three-month picture.
• Lipid panel — triglyceride:HDL ratio above 3 is a useful surrogate for insulin resistance.

In a woman with FPHL, acne, and irregular cycles, an unremarkable androgen panel plus HOMA-IR of 3.2 tells you the follicle problem is downstream of insulin. Treating insulin — through nutrition, resistance training, and in some cases metformin or a GLP-1 — often does more for the hair than topical minoxidil alone.

Vitamin D, B12, and zinc: supporting cast, not soloists

These don't drive FPHL, but deficiencies amplify it:

• 25-hydroxyvitamin D — aim for 40–60 ng/mL; low D is associated with increased telogen shedding.
• Vitamin B12 — particularly relevant in vegetarians, older women, and anyone on long-term PPIs or metformin.
• Zinc — low zinc impairs follicle keratinization; useful to check if diet is restricted.

Don't over-supplement blindly. High-dose zinc, biotin, and vitamin A can each worsen hair loss when overshot, and biotin specifically interferes with thyroid and troponin immunoassays — meaning it can distort the very labs you're trying to interpret.

Menopause status and prolactin: the two often-forgotten checks

Perimenopause and menopause bring a relative rise in androgen effect as estrogen falls, which is why FPHL often accelerates in the mid-40s to mid-50s. Estradiol, FSH, and LH help place a woman in that transition and inform whether hormone therapy is worth discussing.

Prolactin is worth checking once — elevated prolactin can suppress ovarian function, alter the androgen picture, and occasionally points to a pituitary issue that would otherwise be missed.

Putting the panel together — the plain-English version

A thorough baseline workup for female-pattern hair loss would typically include:

• Total testosterone, free testosterone, SHBG, DHEA-S, androstenedione, 17-OHP
• TSH, Free T4, Free T3, TPO and thyroglobulin antibodies
• Ferritin, CBC, serum iron, TIBC, transferrin saturation
• Fasting glucose, fasting insulin, HbA1c, lipid panel
• 25-OH vitamin D, B12, zinc
• Estradiol, FSH, LH, prolactin

It looks like a lot. It fits on one tube rack. And it's the difference between guessing and treating.

The labs worth having before starting a serious FPHL protocol are the ones that answer which hormonal lever is actually pulling. Minoxidil, spironolactone, oral contraceptives, low-dose oral minoxidil, and PRP all have roles — but the right sequence depends on what the panel says.

If you'd like the markers we look at first for hair concerns, we offer this panel through DirectCare AI; you can also bring outside labs to a consult. Either way, the plan should be tuned to your numbers, not to the average woman's.

Editorial disclosure: This article is for informational purposes only and does not constitute medical advice. All treatments at DirectCare AI are prescribed by US-licensed clinicians based on individual medical evaluation. Compounded medications are not FDA-approved and are not reviewed by the FDA for safety, effectiveness, or quality. Always consult a US-licensed clinician before starting or changing any therapy.