Page 938 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Endocrine system 913

VetBooks.ir 6.9

Fig. 6.9 Typical appearance of
a horse with PPID. Note the long
curly hair coat and poor muscling.

6.10
commonly subfertile. Polyuria and polydipsia may
also be present due to either cortisol-induced thirst,
osmotic diuresis secondary to hyperglycaemia and
glycosuria, or diabetes insipidus secondary to pars
intermedia enlargement and encroachment on the
neurohypophysis.
One of the most severe problems experienced
by affected horses is recurrent laminitis, fur-
ther complicated by a predisposition to develop
sole abscesses. Horses with PPID are more than
5 times more likely to develop laminitis than other
horses (Fig. 6.11). They may also have trouble Fig. 6.10 Hyperhydrosis in a horse with PPID.
overcoming other infections such as pneumonia, Sweating is present despite a relatively normal haircoat.
tooth root abscesses and sinusitis. Wounds tend to
heal more slowly than in healthy horses. In very 6.11
advanced cases, circling, blindness and seizure
activity have been described. These clinical signs
are likely caused by expansion of the pituitary
gland and exertion of pressure on the optic chiasm
and hypothalamus.

Differential diagnosis
The appearance of horses with advanced PPID
is fairly unique; however, in less advanced cases,
the clinical picture can be less obvious. The main
differential diagnosis for horses that have chronic
episodes of unexplained laminitis would be equine
metabolic syndrome (EMS). Hair coat abnor-
malities can also be associated with thyroid dis- Fig. 6.11 Lateral radiograph of the distal forelimb
ease, but horses with PPID have normal thyroid of a pony with PPID and insulin resistance. Note the
function. rotation and pedal osteitis at the tip of P3.