“When used topically, nanogram level doses, nearly 1,000 times lower than standard oral doses, have shown significant regrowth potential.”
— Dr. Blake Bloxham, Chief Medical Officer at Anagen and HairDAO
Hair loss can be triggered by genetics, hormones, and health conditions, but one often-overlooked factor is thyroid function. Thyroid hormones, namely T3 and T4, help set the pace for hair-follicle stem-cell activation, matrix cell proliferation, and how long follicles stay in the growth (anagen) phase. Too little hormone slows follicle activity and shortens anagen; too much can push the cycle into overdrive, accelerating turnover and still resulting in shedding. That’s why both ends of the thyroid spectrum can leave extra strands on your brush by day’s end.
Now, preclinical research, and an observational study, suggest that topical liothyronine (T3), the active thyroid hormone, at extremely low doses could be a useful addition for men and women with thinning hair.
What Is Liothyronine (T3) and How Does It Affect Hair?
Liothyronine is the synthetic form of T3, the biologically active form of thyroid hormone created when the body converts T4 (thyroxine) into T3. This conversion matters because T3 directly regulates metabolism, drives cell growth and repair, and helps maintain healthy hair-follicle cycling.
When T3 is low, whether from hypothyroidism, poor T4 to T3 conversion, or under-replacement, the anagen phase shortens, hair shafts thin, and more follicles shift into telogen (the resting phase). The opposite is also true: hyperthyroidism or over-replacement accelerates the cycle, pushing follicles through growth too quickly and triggering diffuse telogen effluvium. In either case, shedding usually shows up 6–12 weeks after the imbalance or dose change, and it tends to improve once thyroid levels return to a stable state.
Important note: Topical T3 is being explored as a local growth stimulator for stubborn thinning; it isn’t a substitute for managing a thyroid disorder.
How Topical T3 Works for Hair Regrowth
According to Dr. Bloxham, “When T3 is applied at a concentration of 6.5 nanograms per milliliter, we’ve seen strong anecdotal and observational data indicating that it can stimulate meaningful hair regrowth.”
Mechanistically, ultra-low-dose topical T3 appears to:
Prolong the anagen phase, so hair grows longer before shedding.
Boost follicle metabolism, increasing the energy available for hair production.
Influence growth biomarkers, triggering pro-growth molecular signaling.
In a HairDAO-supported preclinical collaboration with Prof. Ralf Paus (University of Miami), triiodothyronine (T3) and thyroxine (T4) prolonged hair-shaft elongation and anagen duration in ex vivo human scalp-skin and isolated follicle cultures. Treatment also upregulated keratin 15 (K15), a marker linked to epithelial stem-cell function, and FGF7 (keratinocyte growth factor), a known promoter of hair growth whose inhibition suppresses it among other key markers.
How to Use Topical Liothyronine for Hair Loss
Application guidelines (per Dr. Bloxham):
Concentration: 6.5 nanograms per milliliter
Volume: 1 mL once daily
Method: Gently massage for ~3 minutes into the scalp, ideally after a shower or when hair is slightly damp for better absorption
Consistency: Daily use for at least six months is needed to assess regrowth.
Who Might Benefit from Topical T3?
Topical T3 may be suitable for:
Hair loss treatment for men with androgenetic alopecia who want an additional growth stimulator.
Hair loss treatment for women experiencing thinning
People who have mild or subclinical hypothyroidism impacting hair growth.
Ideal as part of a multi-therapy plan or as a standalone treatment.
Safety and Side Effects
At the nanogram-level doses used topically, our observational data show no reported side effects and no meaningful changes in serum T3/T4, suggesting localized action without systemic disruption. Because this is a compounded, off-label therapy, it should still be used under medical supervision.
For context, higher-dose oral liothyronine can cause hyperthyroid-type effects (palpitations, tremor, anxiety/insomnia; with chronic overtreatment, risks like arrhythmias or lower bone density). At the ultra-low topical dose, systemic exposure is minimal and side effects are highly unlikely, and to date we haven’t observed any in our patients.
Also keep in mind that hair loss is often multifactorial. Alongside thyroid status, rule out common telogen triggers (illness, major stress, crash dieting), iron deficiency (check ferritin), and meds that can cause shedding. If androgenetic alopecia is also in the mix, pairing your thyroid plan with minoxidil and, where appropriate, finasteride, can raise the ceiling on visible density.
Will I Shed When Taking Topical T3 for Hair Growth?
Topical T3 is a new approach to treating hair loss, and while it is designed to act locally at ultra-low doses, there have been anecdotal reports of shedding, similar to what’s seen with other effective hair loss treatments. That makes sense physiologically, since changes in thyroid hormone levels are a well-established trigger for telogen effluvium. If shedding occurs, it’s usually temporary and tends to improve over several months as hormone signaling and hair cycles stabilize.
How to Get Topical T3 for Hair Loss
Topical liothyronine is not FDA-approved for hair loss and is only available through a custom compounded prescription. If your physician deems you an appropriate candidate, you can access it by prescription through Anagen.xyz.
FAQ: Topical Liothyronine (T3) for Hair Loss
1. Is topical T3 the same as oral T3 for hypothyroidism?
No, topical doses are about 1,000 times lower and designed for scalp-targeted action.
2. How quickly with T3 for hair growth can I see results?
In observational data, participants saw improvements within several months, but 6–12 months may yield the most noticeable density gains.
3. Is T3 safe for women?
Yes, topical T3 may be an option for women with hair loss, including those who cannot use other systemic treatments.
4. Can T3 be combined with minoxidil or finasteride?
Yes - combining T3 with other topicals can likely create a synergistic effect.
5. Does T3 help if my thyroid levels are normal?
While not certain, it does appear to regrow hair in patients with normal thyroid levels. However, benefits are most pronounced when thyroid function is contributing to hair loss.
Final Thoughts
Topical liothyronine (T3) may be one of the most exciting emerging treatments in hair regrowth science. Early studies and real-world results suggest it can increase hair density and prolong the growth phase without systemic thyroid disruption.
While it’s not FDA-approved, the combination of preclinical research, in vivo observational reports, and safety data make it a promising hair loss solution for men and women - especially those with thyroid-related shedding or stubborn thinning.
References
van Beek N, et al. Thyroid hormones directly alter human hair follicle functions: anagen prolongation and matrix proliferation. J Clin Endocrinol Metab. 2008. Oxford AcademicPubMed
Contreras-Jurado C, et al. Thyroid hormone signaling controls hair follicle stem cell function. Stem Cells. 2015. PMC
Paus R, Ramot Y, Kirsner RS, Tomic-Canic M. Topical L-thyroxine: the Cinderella among hormones in dermatology. Exp Dermatol. 2020. (Review of TH effects on skin/hair; flags telogen effluvium use case.) PMC
Safer JD, et al. Topical triiodothyronine stimulates epidermal proliferation, dermal thickening, and hair growth in mice and rats. Thyroid. 2001. (Foundational in-vivo animal data.) PubMed
Gherardini J, Akhundlu A, Paus R, et al. Topically applied thyroid hormones stimulate hair growth in organ-cultured human scalp skin. bioRxiv preprint. 2024. (Human scalp ex vivo; anagen prolongation & biomarker shifts.) BioRxiv
Gherardini J, et al. Pilot evidence that topically applied triiodothyronine (T3) can stimulate hair growth in human scalp skin. Clin Exp Dermatol. 2025 (ahead of print). (Peer-reviewed pilot from the Paus group.) Oxford Academic
WO2024124206A1 – Topical compositions for treating and preventing hair loss and hair graying. (Original assignees: HairDAO Payments LLC; Cutaneon. Specifies low-dose topical T3 and includes 6.5 ng per 1 mL unit-dose language.) Google Patents
Anagen Topical Thyroid (product page). (Lists Liothyronine (T3) 6.5 ng/mL; supports the formulation details you cite.) anagen.xyz
Cytomel (liothyronine) FDA label. (Notes temporary partial hair loss can occur in the first months of therapy.) FDA Access Data
British Thyroid Foundation. Hair loss and thyroid disorders. (Hypo- and hyper-thyroidism both cause diffuse shedding.) btf-thyroid.org
Dayel SB, et al. Is thyroid dysfunction a common cause of telogen effluvium? Cureus. 2024. (Hyperthyroidism frequently associated with shedding.) PMC
Malkud S. Telogen Effluvium: A Review. J Clin Diagn Res. 2015. (Shedding typically 2–3 months after a trigger; natural history.) PMC
Malkud S, et al. Telogen Effluvium: A Review of the Literature. Cureus. 2020. (Reinforces 2–3 month lag and self-limited course.) PMC
Cleveland Clinic. Telogen Effluvium—Symptoms, Causes, Treatment & Regrowth. (Usual resolution 3–6 months once stabilized.) Cleveland Clinic
Mayo Clinic. Liothyronine (oral): patient monograph. (Early-therapy temporary hair loss counseling.) Mayo Clinic
Bloxham B. T3 for Hair Growth? The science behind our first patented formula. (Video explainer; supports the “nanogram-level topical” positioning.) YouTube
