Evaluation of experimental methods to induce congenital hypothyroidism in guinea pigs for use in the study of congenital hypothyroidism in horses.
OBJECTIVE
To develop a method to reliably induce congenital hypothyroidism in guinea pigs (Cavia porcellus) and assess similarities between the resultant developmental abnormalities and those described in horses with congenital hypothyroidism.


METHODS
35 female guinea pigs and their offspring.


METHODS
Guinea pigs were allocated to control groups or groups treated with a low-iodine diet before and throughout gestation; an s.c. injection of 100 or 200 microCi of radioactive iodine 131 (131I) on day 40 of gestation; or 0.1% propylthiouracil (PTU) continuously in the drinking water, beginning day 3 or 40 of gestation. In all groups, assessments included gestation duration, litter size, proportion of stillborn pups, and laboratory analyses in live pups and dams; postmortem examinations were performed on all pups and dams and selected tissues were examined histologically.


RESULTS
Compared with control animals, pups from dams receiving a low-iodine diet or 131I s.c. had mild changes in their thyroid glands but no grossly or radiographically detectable lesions of hypothyroidism. Pups from dams receiving PTU were often stillborn (24/27 pups) and had enlarged thyroid glands (characterized by large, variably sized follicles of tall columnar epithelium and little or no colloid), an incomplete coat, and radiographically detectable skeletal dysgenesis.


CONCLUSIONS
Many of the lesions detected in guinea pig pups from the experimentally treated dams were similar to those described in foals with congenital hypothyroidism. Experimental induction of congenital hypothyroidism in guinea pigs may be useful for the study of naturally occurring congenital hypothyroidism in horses.
D'Amours
Geneviève H
GH
Department of Veterinary Pathology, Western College of Veterinary Medicine, Saskatoon, SK, Canada, S7N 5B4.
Taylor
Susan M
SM
Olfert
Ernest D
ED
Simko
Elemir
E
Allen
Andrew L
AL
D000818:Animals; D001835:Body Weight; D001842:Bone and Bones / Q000000981:diagnostic imaging; D003409:Congenital Hypothyroidism; D005260:Female; D006168:Guinea Pigs; D006652:Histological Techniques; D006734:Horse Diseases / Q000473:pathology*; D006736:Horses; D007037:Hypothyroidism / Q000139:chemically induced* / Q000473:pathology*; D007455:Iodine / Q000172:deficiency; D007457:Iodine Radioisotopes; D008098:Litter Size; D023421:Models, Animal; D011441:Propylthiouracil; D011859:Radiography; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D007457:Iodine Radioisotopes; D014284:Triiodothyronine; D011441:Propylthiouracil; D007455:Iodine; D013974:Thyroxine