# Transient loss of consciousness in boxer dogs with hypothyroidism: 3 cases (2015–2018)

## TL;DR

Three Boxer dogs with hypothyroidism showed transient loss of consciousness, which improved after treatment with levothyroxine.

## Contribution

This study highlights hypothyroidism as a potential cause of transient loss of consciousness in Boxer dogs.

## Key findings

- Transient loss of consciousness in Boxers was associated with hypothyroidism.
- Levothyroxine treatment resolved or improved the symptoms in all three dogs.
- Second-degree atrioventricular block and sinus bradycardia were observed during an episode.

## Abstract

Three Boxers, two neutered females and one neutered male, aged from seven to eleven years, were presented for investigation of transient loss of consciousness.

In each case, physical examination revealed no significant abnormalities and echocardiography, and electrocardiography did not identify a cause of transient loss of consciousness. Twenty-four-hour electrocardiogram (Holter) monitoring was performed in all three dogs. One dog had an episode of transient loss of consciousness whilst wearing the Holter, during which second-degree atrioventricular block and sinus bradycardia were observed. Based on clinicopathological testing, all three dogs were diagnosed with hypothyroidism. Once hypothyroidism was diagnosed all dogs were started on levothyroxine. In all cases the transient loss of consciousness resolved or improved once the treatment was started.

Hypothyroidism should be considered as a differential diagnosis in Boxers presenting with transient loss of consciousness. Treating hypothyroid Boxers may decrease or resolve the clinical signs.