(E18) Comparison of Hair Characteristics in Equids Affected with Pituitary Pars Intermedia Dysfunction and Aged Controls

Abstract:

Background:
Progressive hair changes associated with Pituitary pars-intermedia dysfunction (PPID) are poorly characterized.

Objectives:
To compare the variations of hair characteristics in PPIDs and aged controls.

Animals:
Fifty-seven client-owned horses and ponies, at least 15-year-old, included over the course of four seasons.

Methods:
At admission, a PPID-clinical score (CS/33), a TRH stimulation test, a shedding score, a jugular hair root density using dermoscopy (cm2), a trichogram assessing anagen (A)/ telogen (T) ratio (%) and mean sternal hair length (cm; on 10 hairs) were performed. Results were analyzed using Shapiro-Wilk and Kruskall-Wallis tests.

Results:
Twenty-six equines harboring hypertrichosis were PPID, 20 presented equivocal results, and 11 were controls. Median CS was statistically higher in PPIDs (17.0 +/-5.7) compared to Equivocals (6.0+/-1.7) and Controls (4 +/-0.7) (p< 0.01). In healthy controls, shedding scores increased physiologically in spring and fall. Jugular hair density and sternal hair length were maximal in winter, A/T ratio increased in fall and was minimal in summer. Median jugular hair density, A/T ratio, and sternal hair length were significantly different between the 3 groups (p< 0,01). Hair changes in the PPID group were characterized by sustained anagen activity, higher hair root density and hair length throughout the year, and a time-lagged shedding score. Equids in the Equivocal group showed variable intermediate hair changes.

Conclusions/clinical importance:
Abnormal shedding and progressive hypertrichosis in PPIDs are characterized by higher hair density, longer hair and sustained anagen hair follicle activity. Further studies are warranted to evaluate the influence of season and breed on haircoat characteristics.