Primary hypoparathyroidism in Dogs (Canis) | Vetlexicon
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Primary hypoparathyroidism

ISSN 2398-2942

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Synonym(s): eclampsia

Introduction

  • Relatively rare.
  • Cause: immune-mediated degenerative or surgical removal of glands.
  • Signs: characterized by hypocalcemia + hyperphosphatemia and either transient or permanent PTH insufficiency.
  • Eclampsia in late pregnancy or lactation Puerperal tetany.
  • Diagnosis: biochemistry.
  • Treatment: calcium and vitamin D supplementation.
  • Prognosis: fair to good with treatment.

Presenting signs

  • Focal muscle twitching or generalized tremors progressing to tetanic spasm and tonic-clonic seizures.
  • Stiff hunched gait or ataxia.
  • Behavioral changes: restlessness, aggressiveness, disorientation.
  • Non-specific signs:
    • Anorexia.
    • Weakness.
    • Listlessness.
    • Vomiting.
    • Diarrhea.
    • Weight loss.

Acute presentation

  • Convulsions and tetany, prolapsed third eyelid.

Age predisposition

Idiopathic hypoparathyroidism

  • 2-5 years old.

Breed/Species predisposition

Idiopathic hypoparathyroidism

  • Small breeds, eg Terrier, Schnauzer.

Pathogenesis

Etiology

  • Spontaneous:
    • Agenesis of parathyroid glands.
    • Atrophy of parathyroid glands with prolonged hypercalcemia Hypercalcemia: overview.
    • Immune-mediated parathyroiditis.
    • Idiopathic: rare ? familial in St. Bernard (may be associated with hypothyroidism Hypothyroidism ).
  • Complication of thyroidectomy: removal of, or damage to, parathyroids.
    One parathyroid gland is sufficient to prevent occurrence of tetany.

Pathophysiology

  • In normal animal release of parathyroid hormone (PTH) from the parathyroid gand is stimulated by a drop in ionized calcium levels.
  • PTH increases serum ionized calcium by increasing:
    • Calcium resorption from glomerular filtrate.
    • Phosphate secretion.
    • Osteoclast function thereby increasing bone resorption.
    • Vitamin D formation.
  • Reduced PTH secretion → decreased serum ionized calcium → increased neuromuscular irritability → tetany and convulsions.
  • Excessive panting and hyperventilation during tetany can → respiratory alkalosis → increased protein-bound calcium and reduced ionized calcium → exacerbation of problem.
  • Pyrexia may be due to increased muscle activity during tetanic spasm.

Timecourse

  • Within days or months of thyroidectomy.
  • May be temporary or permanent.

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.
  • Wisner E R, Penninck D & Biller D S  et al (1997) High resolution parathyroid sonography. Vet Radiol Ultrasound 38 (6), 462-466 PubMed.
  • Bruyette D S & Feldman E C (1988) Primary hypoparathyroidism in the dog - report of 15 cases and review of 13 previously reported cases. JVIM 2 (1), 7-14 PubMed.
  • Kornegay J N, Greene C E, Martin C, Gorgacz E J & Melcon D K (1980) Idiopathic hypocalcemia in four dogs. JAAHA 16 (5), 723-34 PubMed.
  • Sherding R G, Meuten D J, Chew D J, Knaack & Haupt K H (1980) Primary hypoparathyroidism in the dog. JAVMA 176 (5), 439-44 PubMed.