Thyroid-stimulating hormone and total thyroxine concentrations in euthyroid, sick euthyroid and hypothyroid dogs

Area of Science:

• Veterinary Endocrinology
• Canine Health
• Diagnostic Medicine

Background:

• Canine hypothyroidism is a common endocrine disorder.
• Accurate diagnosis relies on a combination of clinical signs and laboratory tests.
• Canine thyroid-stimulating hormone (cTSH) is a key regulator of thyroid function.

Purpose of the Study:

• To evaluate the diagnostic utility of canine thyroid-stimulating hormone (cTSH) measurements in various clinical conditions.
• To establish a reference range for basal cTSH concentrations in euthyroid dogs.
• To assess the response of cTSH to thyroid-releasing hormone (TRH) stimulation in specific cases.

Main Methods:

• Measurement of basal cTSH concentrations in 72 dogs across different clinical categories.
• Classification of dogs based on history, clinical signs, laboratory results, and therapeutic response.
• TRH stimulation tests were performed in some cases to assess cTSH response.

Main Results:

• A reference range for basal cTSH was established (0-0.41 ng/ml) from 41 euthyroid dogs.
• Six of nine hypothyroid dogs exhibited elevated basal cTSH; three were within the normal range.
• Sick euthyroid syndrome and non-thyroidal treatment influenced cTSH levels, highlighting diagnostic complexities.

Conclusions:

• Canine TSH measurement is a valuable supplementary diagnostic tool for suspected canine hypothyroidism.
• Dynamic testing, such as TRH stimulation, remains essential for confirming a hypothyroidism diagnosis.
• Interpretation of cTSH requires consideration of the dog's overall clinical status and concurrent treatments.