ENDOCRINOLOGY
Diagnosis of
Hyperadrenocorticism
Sandy May BVSc (Hons),MMed Vet (Clin Path)
Vetdiagnostix. Cape Town Branch. Tel: 021 910 2243
Hyperadrenocorticism (HAC) occurs as a result of hyperplasia or neoplasia (Adrenal dependent hyperadrenocorticism - ADH) of the zona fasiculata of the adrenal cortex resulting
in overproduction of cortisol.
Hyperplasia of the adrenal gland results from an adenoma of the pars distalis or pars intermedia of the
pituitary gland (pituitary dependent hyperadrenocorticism - PHD).
Serum cortisol has a negative feedback effect on the
production of ACTH and CRH by the pituitary and the
hypothalamus. ACTH also has a negative feedback effect on the hyopthalamus. In dogs the secretion of
ACTH is pulsatile with 6-12 peaks in a day.5
Any breed can develop hyperadrenocorticism but in
general middle aged to older small breed dogs develop PDH and older large breed dogs develop AD