Topical triiodothyronine stimulates epidermal proliferation, dermal thickening, and hair growth in mice and rats.

Topical triiodothyronine stimulates epidermal proliferation, dermal thickening, and hair growth in mice and rats.

Safer JD, Fraser LM, Ray S, Holick MF.

Department of Medicine, Boston University School of Medicine, Massachusetts 02118, USA. jsafer@bu.edu

The skin is a classic target tissue for thyroid hormone action. Although the histology of skin in hypothyroid states is well documented, the literature contains little assessment of skin in thyrotoxic states. In light of the paucity of information on skin under the influence of excess thyroid hormone, we investigated the direct effect of thyroid hormone on skin. Triiodothyronine (T3) was applied topically daily in liposomes to SKH-1 hairless mice for 7 days and to CD rats for 2 weeks. There was a dose-dependent increase in epidermal proliferation, dermal thickening, and hair growth in T3-treated animals. Mice that received 3.8 microg of T3 had 42% more hairs per millimeter than controls (p < 0.01), hair length that was 1,180% longer (p < 0.001), 49% greater epidermal 3H-thymidine incorporation (p < 0.01), and 80% more 5-bromo-2'-deoxyuridine (BrdU) stained cells (p < 0.05). Rats receiving 12.8 microg T3 had 48% greater dermal thickness than controls (p < 0.001), 26% greater epidermal thickness (p < 0.001), 85% more hairs per millimeter (p < 0.005), and 130% greater 3H-thymidine incorporation into the epidermis (p < 0.01). Thus, topically applied thyroid hormone has dramatic effects on both skin and hair growth. These observations offer a new strategy for developing thyroid hormone and its analogues for treating disorders of skin and hair growth.

Smurfy wrote:Immediate thoughts:

Why would this work? Does the blood flowing to the follicles not contain sufficient amounts of these hormones? and/or... Is there just bad micro-circulation leading to insufficient levels of it? Perhaps it's the final stage in the HPA axis link.

Internal conversion is a must, but this..... for our own sanity, we need to try this haha.

aThat's insane, I have never thought of the possibility of topical thyroid hormone ... we've all be so caught up on internal conversion, the gland itself, hormone interactions, etc that we've obviously overlooked some of the seriously obvious. Great post that I think shouldn't disappear into site.

Context: Both insufficient and excess levels of thyroid hormones (T3 and T4) can result in altered hair/skin structure and function (e.g. effluvium). However, it is still unclear whether T3 and T4 exert any direct effects on human hair follicles (HFs), and if so, how exactly human HFs respond to T3/T4 stimulation.

Objective: Our objective was to asses the impact of T3/T4 on human HF in vitro.

Methods: Human anagen HFs were isolated from skin obtained from females undergoing facelift surgery. HFs from euthyroid females between 40 and 69 yr (average, 56 yr) were cultured and treated with T3/T4.

Results: Studying microdissected, organ-cultured normal human scalp HFs, we show here that T4 up-regulates the proliferation of hair matrix keratinocytes, whereas their apoptosis is down-regulated by T3 and T4. T4 also prolongs the duration of the hair growth phase (anagen) in vitro, possibly due to the down-regulation of TGF-β2, the key anagen-inhibitory growth factor. Because we show here that human HFs transcribe deiodinase genes (D2 and D3), they may be capable of converting T4 to T3. Intrafollicular immunoreactivity for the recognized thyroid hormone-responsive keratins cytokeratin (CK) 6 and CK14 is significantly modulated by T3 and T4 (CK6 is enhanced, CK14 down-regulated). Both T3 and T4 also significantly stimulate intrafollicular melanin synthesis.

Conclusions: Thus, we present the first evidence that human HFs are direct targets of thyroid hormones and demonstrate that T3 and/or T4 modulate multiple hair biology parameters, ranging from HF cycling to pigmentation.

anthonyspencer54 wrote:Amazing findings guys. Thanks for the post ABC. I am interested in trying to formulate a topical also. Is cytomel only available via prescription. If not, where are you purchasing from, if you are alright saying.

Especially seeing as they were only treated for 1-2 weeks. I have quite a few cytomel tabs, so I will try to make a topical.

LawOfThelema wrote:

Especially seeing as they were only treated for 1-2 weeks. I have quite a few cytomel tabs, so I will try to make a topical.

Murine metabolism is faster than human metabolism. Mice grow hair faster, are more suceptible to tumor growth, and have shorter lifespans than humans. This is account of faster metabolism. What grows in 2 weeks on a mouse does not correspond to fast action in human beings.

LawOfThelema wrote:yeah. a rule of thumb is size inverse with metabolism. smaller mammals tend to have shorter life spans, faster to reach maturity, faster growth rates, etc. probably holds for animals generally.