Canine Primary Hypothyroidism and Apprication and Evaluation of Thyroid Function Tests

Abstract

Primary hypothyroidism was diagnosed in a 4-year-old golden retriever bitch with a disturbance in gait as a chief complaint. This bitch showed bilateral alopecia, hyperpigmentation, thicking and wrinkling of the skin, seborrhea, and myxedema-like edematous skin. Anemia, hypercholesteremia, and low values of serum thyroxine (0.4 μg/dl) and triiodothyronine-binding capacity index (0.88) were revealed. Serum protein-binding iodine was normal (2.8 μg/dl), as compared with that in 15 normal dogs (3.3±1.58 μg/dl). The values of these three thyroid function tests (T4, TBC index and PBI) showed no significant changes 24 hours after TSH (5-10 IU) stimulation, as compared with those before stimulation. In contrast, 5 normal dogs exhibited a significant increase (averaging 2.8 times) in PBI response to TSH stimulation. The spread of the iodine preparation on the skin surface boosted the PBI value (averaging 5.3 times).
Treatment consisted of sodium L-tetraiodothyronine replacement at a dosage of 5-7.5 μg/kg, once a day. Clinical response was good to hormone therapy within 1 month. The atrophic thyroid gland was characterized by the severe destruction of follicles and replacement of most of the thyroid by fibrous connective tissue.