Retrospective Study on Hyperthyroidism in Guinea Pigs in Veterinary Practices in Germany

Abstract

Guinea pigs with a total thyroxine (TT4) value >66.9 nmol/l (>5.2 µg/dl) were selected from the database of a private diagnostic laboratory. The submitting veterinarians were sent standardized questionnaires in order to assess background information on clinical signs, therapy and the success of the therapy in these cases. Information from 40 cases was evaluated. Eighteen of these animals were male, 7 of which were castrated. Twenty-one animals were intact females. No sex was provided in 1 case. Increased blood TT4 values were found predominantly in elderly guinea pigs. The median age of affected animals was 5 years. The clinical signs most consistently found were weight loss associated with a constant or increased appetite. Two thirds of the animals had palpable masses on the ventral neck which were considered to belong to the thyroid gland. These masses did not correlate with increased TT4 concentrations in the blood. Ninty-two percent of the animals (36/38) were treated with thiamazole or carbimazole while the thyroid gland was surgically removed in 6 cases. In 19 animals, TT4 was evaluated again after treatment and the value was reduced in 12 (12/19) of those cases. The median drop in TT4 concentrations was 29.6 nmol/l (2.3 µg/dl) (range 5.2 to 128.7 nmol/l, respectively, 0.4 to 10.0 µg/dl).The veterinarians reported clinical improvement in 48 % (13/27) of the animals. Moderate clinical improvement to complete recovery was observed in 3 (3/6) of the animals treated surgically. One continued to receive thyreostatic drugs, 1 did not clinically improve and 1 died.