Thyroid hormones directly alter human hair follicle functions

Full Study here: http://jcem.endojournals.org/cgi/rapidpdf/jc.2008-0283v1

Abstract:

J Clin Endocrinol Metab. 2008 Aug 26.

: Anagen prolongation, and stimulation of both hair matrix keratinocyte proliferation and hair pigmentation.

Context: Both, insufficient and excess levels of thyroid hormones (T3, T4) can result in altered hair/skin structure and function (e.g. effluvium). However, it is still unclear whether T3/T4 exert any direct effects on human hair follicles (HFs), and if so - how exactly human HFs respond to T3/T4 stimulation. Objective: to asses the impact of T3/T4 on human hair follicle in vitro. Methods: Human anagen HFs were isolated from skin obtained from females undergoing face-lift surgery. Hair follicles from euthyroid females between 40 and 69 years (average: 56 years) were cultured an 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, while their apoptosis is downregulated by T3 and T4. T4 also prolongs the duration of the hair growth phase (anagen) in vitro, possibly due to the down-regulation of TGFbeta2, the key anagen-inhibitory growth factor. Since we show here that human HFs transcribe deiodinase genes (D2 and D3), they may be capable of converting T4 to T3. Intrafollicular immunoreactivity (IR) for the recognized thyroid hormone-responsive keratins CK6 and CK14 is significantly modulated by T3 and T4 (CK6: 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.

And again, IH was years ahead of the curve! haha

CS-Thanks for the study. Have you actually seen men that loss hair due to a thyroid problem?

GoodThings - Yes, it definitely happens to men. Women suffer from thyroid much more, yet they tend to be more vulnerable to it and are probably more likely to be checked for it.