Hypothyroidism in foals.

The research paper focuses on the condition of hypothyroidism in foals, observed in three different cases in New Zealand. The researchers discuss the effects of the disease, their observations of the affected foals, treatments applied, and the implications for other animals.

Cases Presented

• Three different cases of hypothyroidism in foals were observed in New Zealand within a span of two years.
• The symptoms included poor coordination, lack of interest in suckling, cold skin and mouth, and below-normal rectal temperature.
• One of the foals died within hours of birth and upon autopsy, the foal’s only abnormality was a colloid goitre with flattened epithelium. This was a marked contrast from the small follicles and cuboidal epithelium of a healthy newborn foal.
• The condition of the other two foals improved significantly after treatment with thyroid hormones.

Causes of Hypothyroidism in Foals

• The researchers mention that hypothyroidism usually occurs in foals whose mothers are fed an iodine-deficient diet.
• The periods of rapid growth and cell differentiation in pre and post-natal life are associated with high thyroxine requirement, making iodine integral to foal health.
• The research also suggests that overconsumption of iodine during the mare’s pregnancy can result in hypothyroidism in the foal.
• The use of iodine competitors or antagonists in horse feed such as linseed meal, white clover, perennial rye-grass, new pasture, were also found to be a cause.
• In addition, the researchers put forth the possibility of transmission of a thyroid antibody in colostrum from mother to newborn, similar to the transplacental passage of thyroid antibodies in humans.

Implications and Recommendations

• The symptoms of hypothyroidism in foals can closely resemble those of prematurity, and can include neuromuscular incompetence, reduced thermogenic ability and musculoskeletal dystrophy in newborns and defective growth and goitre in older foals.
• Given that excessive administration of iodine or thyroid hormones could worsen the condition, the researchers remind that testing, via measurement of thyroid hormone levels in plasma, is critical before initiating treatment.
• The purpose of the paper is to increase awareness among vets about hypothyroidism in foals, in order to ensure early detection and appropriate treatment.