Pituitary Gland - Pathology
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Anatomy and Physiology
Anatomy and Physiology of the pituitary gland can be found here.
General Pathological Principles
Two major changes can occur in an endocrine gland:
- Failure of hormone production:
- Destruction or lack of cells.
- Lack of trophic drive.
- Overproduction of hormone:
- Hyperplasia or neoplasia.
- Excessive trophic drive.
Pituitary Hypofunction
Congenital Panhypopituitarism
Pituitary Cysts
Pituitary Neoplasia
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.
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.