Search Results

Abstract

Objective—To evaluate the correlation between plasma α-melanocyte-stimulating hormone (α-MSH) concentration and body mass index (BMI) in healthy horses.

Animals—82 healthy horses.

Procedure—Plasma α-MSH concentration was determined by radioimmunoassay. At the time blood samples were collected, body condition scores (BCS) were determined and measurements of girth circumference, body length, and height were obtained. Weight was estimated by use of the following formula: estimated weight (kg) = [girth (cm)² × length (cm)]/11,877. Body mass index was calculated as estimated weight (kg)/height (m)².

Results—A correlation was found between BMI and BCS (r _s = 0.60 [95% confidence interval (CI), 0.44 to 0.73]). A weak correlation was found between plasma α-MSH concentration and BMI (r _s = 0.25 [95% CI, 0.03 to 0.45]) and BCS (rs = 0.26 [95% CI, 0.04 to 0.46]). A correlation was found between plasma α-MSH concentration and BMI in horses ≥ 10 years old (r _s = 0.49 [95% CI, 0.20 to 0.69]) but not in horses < 10 years old (r _s = –0.04). Horses in the upper quartile of BMI had significantly greater plasma α-MSH concentration (median, 9.1 pmol/L; range, 2.0 to 95.3 pmol/L) than horses in the lowest quartile of BMI (median, 7.0 pmol/L; range, 3.6 to 15.7 pmol/L).

Conclusions and Clinical Relevance—A correlation exists between plasma α-MSH concentration and BMI in horses. Further study is required to determine whether melanocortin receptor defects underlie this correlation or, alternately, whether plasma α-MSH concentration is simply a correlate of adiposity. (Am J Vet Res 2004;65:1469–1473)

Abstract

Objective—To determine prevalence and clinical features of pituitary pars intermedia dysfunction (PPID) in horses with laminitis.

Design—Case series.

Animals—40 horses with laminitis.

Procedures—Horses with laminitis that survived an initial episode of pain and were not receiving medications known to alter the hypothalamic-pituitary-adrenal axis were tested for PPID by evaluation of endogenous plasma ACTH concentration. Signalment, suspected cause, month of onset and duration of laminitis, Obel grade of lameness, pedal bone rotation, physical examination findings, results of endocrine function tests, treatment, outcome, and postmortem examination findings were recorded.

Results—Prevalence of PPID as defined by a single high plasma ACTH concentration was 70%. Median age of horses suspected of having PPID (n = 28) was 15.5 years, and median age of horses without PPID (12) was 14.5 years. Laminitis occurred most frequently in horses with and without suspected PPID during September and May, respectively. Chronic laminitis was significantly more common in horses suspected of having PPID. In horses suspected of having PPID, the most common physical examination findings included abnormal body fat distribution, bulging supraorbital fossae, and hirsutism. Five horses suspected of having PPID had no clinical abnormalities other than laminitis. Seventeen horses suspected of having PPID that were treated with pergolide survived, and 3 horses that were not treated survived.

Conclusions and Clinical Relevance—Evidence of PPID is common among horses with laminitis in a primary-care ambulatory setting. Horses with laminitis may have PPID without other clinical signs commonly associated with the disease. (J Am Vet Med Assoc 2004;224:1123–1127)