Congenital hypothyroidism and concurrent renal insufficiency in a kitten

Medical Management of Dental Abnormalities Related to Congenital Hypothyroidism in a Cat

A 5-month-old intact male domestic shorthair cat presenting for routine vaccinations was diagnosed with congenital hypothyroidism. His primary presenting symptom was incomplete dentition with delayed dental eruption. Congenital hypothyroidism was confirmed by baseline thyroxine (T4), free T4, and thyroid-stimulating hormone testing. The cat was treated with oral thyroid hormone supplementation and 16 weeks after initiation of therapy the cat was clinically normal with age-appropriate dentition. No surgical intervention was necessary to achieve normal dental eruption.

Evaluation of Weight Gain, Clinicopathological and Radiographic Changes after Early Diagnosis and Treatment of Congenital Hypothyroidism in Cats

Congenital hypothyroidism is uncommon in cats. This case report describes weight gain, clinicopathological and radiographic changes after early diagnosis and treatment of congenital hypothyroidism in three British shorthair cats’ siblings. Data were assessed at 53 (diagnosis), 83, 185 and 365 days of age. Correlations between serum insulin-like growth factor-1 (IGF-1) and body weight, levothyroxine dose, total thyroxine, and thyroid-stimulating hormone concentrations were evaluated. The body weights of the congenital hypothyroid kittens were compared with those of their two healthy siblings and British shorthair kittens of the same age. At diagnosis, the congenital hypothyroid kittens showed a significantly lower body weight compared to the healthy siblings (p = 0.03). After diagnosis, oral levothyroxine supplementation was started. The difference in body weight was no longer observed after one month of treatment. The clinical signs, clinicopathological and radiographic abnormalities ameliorated after one month of treatment. IGF-1 concentration was significantly positively correlated with body weight (rs = 0.80, p < 0.002). In conclusion, resolution of the clinical signs, achieving a consistent within-breed weight, and improvement of the clinicopathological and radiographic parameters demonstrated the importance of the early diagnosis and treatment of feline congenital hypothyroidism.

Severe calcification of systemic blood vessel walls caused by continuous hypercalcemia in a cat with congenital hypothyroidism

A 97-day-old male Japanese domestic cat was diagnosed as congenital hypothyroidism. During the treatment, continuous hypercalcemia was detected. Although fluid therapy was performed, the cat died at the age of 1785 days. At autopsy, both parathyroid glands were enlarged, and elastic arterial walls were increased in thickness and hardness. Histopathological examination revealed hyperplasia of both parathyroid glands and interstitial fibrosis of bilateral kidneys. Severe calcification of the tunica media and tunica externa in systemic elastic and muscular arteries were also observed. These calcifications were considered to be due to renal secondary hyperparathyroidism. In the present case, hypothyroidism might have caused hyperparathyroidism through renal failure. In veterinary medicine, this is the first reported case of hypothyroidism accompanied with hyperparathyroidism.

Primary goitrous hypothyroidism in a young adult domestic longhair cat: diagnosis and treatment monitoring

Case summary

Primary goitrous hypothyroidism was diagnosed in a 12-month-old cat examined because of small stature, mental dullness, severe lethargy, generalized weakness and gait abnormalities. Radiographs of the long bones and spine revealed delayed epiphyseal ossification and epiphyseal dysgenesis. Diagnosis of primary hypothyroidism was confirmed by low serum concentrations of total and free thyroxine (T4) with high thyroid-stimulating hormone (TSH) concentrations. Thyroid scintigraphy revealed severe enlargement of both thyroid lobes, as evidenced by a seven-fold increase in calculated thyroid volume above the reference interval. In addition, this bilateral goiter had an extremely high radionuclide uptake, about 10-fold higher than the normal feline thyroid gland. Treatment with twice-daily levothyroxine (L-T4), administered on an empty stomach, resulted in increased alertness, playfulness, strength and improvement in gait, as well as an increase in body length and weight. L-T4 replacement also led to normalization of serum thyroid hormone and TSH concentrations, and complete resolution of goiter.

Relevance and novel information

Spontaneous hypothyroidism is rarely reported in cats, with congenital hypothyroidism in kittens diagnosed most frequently. Despite the fact that this cat was a young adult, it likely had a form of congenital hypothyroidism caused by dyshormonogenesis (defect in thyroid hormone synthesis) that led to compensatory development of goiter. In hypothyroid cats, treatment with L-T4 is best given twice daily on an empty stomach to ensure adequate absorption. Normalization of serum TSH and shrinkage of goiter, as well as improvement in clinical signs, is the goal of treatment for cats with goitrous hypothyroidism.