Pituitary Neoplasia

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Tumours within the pituitary fossa may be functional and sectrete trophic factors. However, more commonly they are non-functional and are space-occupying lesions. Pressure on neighbouring structures causes clinical signs, for example:

  • Pressure on the optic chiasma produces ocular signs.
  • Pressure on the hypothalamus may lead to Frohlich's adiposogenital syndrome.
  • Pressure on the neurohyposphysis may lead to failure of ADH secretion. This will allow large volumes of water to be lost form the kidney; Diabetes Insipidus.
Pituitary neoplasia. Courtesy of A. Jefferies

Neoplasia may be derived from:

  • Pituitary itself.
  • Surrounding brain tissue.
  • Ependyma.

Pituitary neoplasia in the horse

Neoplasia usually occurs in the pars intermedia of the anterior pituitary and compresses the hypothalamus.

Clinical signs:

  • Polyuria and polydipsia.
  • Increased appetite reulting in increased food intake and downregulation of insulin receptors. This leads to a hyperglycaemia.
  • Somnolence.
  • Muscle wekaness.
  • Hirsutism.
  • Hyperhidrosis.