Thyroid hormone receptor beta 1 is expressed in the human hair follicle

To understand better the mechanisms by which thyroid hormone can exert its effects on the hair follicle, we looked for the expression of members of th e thyroid hormone receptor (TR) family in human hair follicles. Immunoreact ive TRs were detected in both dermal and epithelial compartments of the hum an pilosebaceous unit. Using reverse transcriptase-polymerase chain reactio n, we established that TR beta 1 was the predominant form of TR expressed i n the human hair follicle. In addition, we investigated the effects of 3,3' ,5-triiodo-L-thyronine (T3) on the survival of human hair follicles in vitr o, to understand the role of this thyroid hormone on hair follicle homeosta sis. A physiological level of free T3 significantly enhanced human hair sur vival in vitro.