00695-A: Estrogen Receptor Antagonist and Hair Regrowth in Dogs with Follicular Arrest (Alopecia X)

Abstract

Follicular arrest (also known as Alopecia X, adrenal hyperplasia-like syndrome, growth hormone responsive alopecia, and others) is a common condition seen in Pomeranians and other "plush-coated" breeds. While systemic illness is not associated with this disease, the loss of hair is dramatic and of concern to the owner. The pathomechanism of the hair loss is not known, but appears to be related to an abnormality in the hair follicle's ability to cycle properly. Once the hair is in telogen or resting phase of the hair cycle, new hair growth does not occur. Recently there has been the recognition of an estrogen receptor pathway that appears to regulate the transition of the hair from resting to active growth. We hypothesize that dogs with follicular arrest have increased activity of estrogen receptors in hair follicles preventing the hair follicles from cycling normal. A potent estrogen receptor blocker has been developed for treating women with breast cancer. It has been extensively tested in dogs and has no side effects except for those related to anti-estrogen activity such as reduction in fertility. Therefore, we would like to test the ability of this drug to cause hair regrowth in Pomeranian dogs with follicular arrest. This will be a pilot study in which 5 dogs with alopecia will receive an intramuscular injection of the active drug (fulvestrant) monthly for 2 months and 5 will receive placebo. The dogs will be evaluated for hair regrowth in 1 month intervals. If hair regrowth occurs, the dogs which received placebo will be offered the active drug. CBC, chemistry panel, and urinalysis will be monitored prior to receiving the first injection, and monthly for 2 months.

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