ISSN 2398-2985      

Hyperthyroidism

6guinea pig

Introduction

  • Cause: excessive secretion of thyroid hormones by the thyroid gland.
  • Signs: weight loss, poor body condition, normal or increased appetite, polydipsia and polyuria, hyperactivity, nervousness, poor fur condition often with progressive alopecia over the dorsum and inguinal areas, soft feces or diarrhea, palpable thryoid gland(s), tachycardia (often heart murmur, arrhythmia), hyperesthesia.
  • Diagnosis: elevated serum thyroxine (T4), ultrasound examination, fine-needle aspiration and cytologic examination of palpable thyroid masses (ultrasound-guided), nuclear scintigraphy (confirmatory and most precise).
  • Treatment: methimazole or carbimazole, radioactive iodine treatment, thyroidectomy.
  • Prognosis: if malignant changes, may develop metastasis especially to the lungs so prognosis is poor. For non-malignant, prognosis with treatment is good.

Pathogenesis

Etiology

  • Thyroid glands affected with hyperplasia, adenoma, and carcinoma may secrete excessive thyroid hormones: tyroxine and triiodothyronine.
  • In one study, 55% of all thyroid pathologies were adenocarcinomas.

Pathophysiology

  • Changes to the thyroid glands lead to excessive secretion of thyroid hormones.
  • Excessive circulating thyroid hormones leads to:
    • Increase in metabolic rate.
    • Exacerbate effects on the sympathetic nervous system.

Timecourse

  • Depending on thyroid gland pathology - likely slow onset if hyperplastic, but faster if malignant.

Epidemiology

  • Prevalence in one study was 4.6% of a guinea pig population.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Mayer J, Wagner R, Mitchell M A & Fecteau K (2013) Use of recombinant human thyroid-stimulating hormone for evaluation of thyroid function in guinea pigs (Cavia porcellus). J Am Vet Med Assoc 242 (3), 346-349 PubMed.
  • Mayer J, Wagner R & Taeymans O (2010) Advanced diagnostic approaches and current management of thyroid pathologies in guinea pigs. Vet Clin Exot Anim 13 (3), 509-523 PubMed.

Other sources of information

  • Pignon C (2013) Hyperthyroidism. In: Clinical Veterinary Advisor Birds and Exotic Pets. Eds: Mayer J & Donnelly TM. Elsevier. pp 260-261.

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