Vol. 7, Issue 1 (2018)

Author(s):
Manu Jaiswal, PC Shukla, Amita Tiwari, Devendra Gupta, Brejesh Singh, Priya Maravi, Anjali Singh, DS Khare, Rakshanda Bhagat and Amir Amin Sheikh

Abstract:
Hypothyroidism is the most frequently diagnosed endocrinopathy in dogs characterised by diminished production of the thyroid hormones i.e. thyroxine (T4) and thyronine (T3) and is of three types: primary hypothyroidism (>95 percent), secondary hypothyroidism and tertiary hypothyroidism. In adult dog, the most consistent clinical signs of hypo-thyroidism are due to decreased cellular metabolism and dermatological manifestations. Additional clinical signs may affect the neuromuscular system, gastrointestinal system and reproductive system. The presence of appropri¬ate clinical signs is imperative, especially when relying on baseline thyroid hormone concentrations for the diagnosis. Identification of mild non-regenerative anaemia on the complete blood count and an increased serum cholesterol concentration on a serum biochem¬istry panel adds further support for hypothyroidism. Low serum T4, free T4 and increased serum TSH concentrations in a dog with appropriate clinical signs and clinic-pathological abnormalities strongly support the diagnosis of hypothyroidism, especially if systemic illness is not present. Initial treatment of choice, regardless of the underlying cause of hypothyroidism is synthetic L-T4 sodium. The recommended initial dose for healthy hypothyroid dog is 0.02 mg/kg PO every 12 hours. The plasma half-life of L-T4 sodium in dogs ranges from 9 to 14 hours and depends on the dos¬age and frequency of administration, with higher dosages and more frequent administration associated with a shorter half-life of L-T4 sodium. With appropriate therapy, all of the clinical signs and clinic-pathological abnormalities associated with hypo-thyroidism should resolve.