Page 35 - VetCPD Jnl Volume 7, Issue 4

of the zona fasciculata and the zona reticularis.Technically this is a type
of isolated hypocortisolaemia because glucocorticoid deficiency is present but mineralocorticoid deficiency is spared.
Clinical signs
Clinical signs and clinico-pathological features of hypoadrenocorticism are explained by the functions of the deficient hormones. Deficiency of the mineralocorticoid aldosterone typically leads to hyponatraemia, hyperkalaemia, acidaemia and hypovolaemia whereas cortisol deficiency typically results
in anorexia, weight loss, anaemia, hypoalbuminaemia and hypoglycaemia. Clinical signs range from mild to severe, can be acute or chronic and in the chronic cases can wax and wane.A summary of clinical signs and possible clinio-pathological findings can be seen in Table 1.
As mentioned, clinical signs can be
Adrenal Cortex
Zona glomerulosa Mineralocorticoids (aldosterone)
Zona fasciculata Glucocorticoids (cortisol)
Zona reticularis Androgens
Adrenal medulla
Catecholamines
Figure 1: The adrenal gland and corresponding hormones that are released.
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with isolated hypocortisolaemia may demonstrate only hypoalbuminaemia and hypocholesterolaemia with or without hypoglycaemia.
There are several recent reviews which cover the pathogenesis, diagnosis and treatment of canine hypoadrenocorticism
in more detail and the interested reader
is directed to these for more information (Klein & Peterson 2010; Spence et al. 2018).
non-specific, and they frequently respond
to symptomatic treatment before they
recur. Clinicians should be especially
vigilant if bradycardia is identified
(despite evidence of hypovolaemia), or
if more severe hypovolaemia is present
than would typically be expected from gastrointestinal signs. Clinicians should also be mindful of sudden deterioration following an apparently stressful event. It should also be noted that dogs
Only
Figure 2: The HPA axis. Cortisol exerts negative feedback on the hypothalamus and anterior pituitary gland.
AB
Figure 3: A: Primary hypoadrenocorticism (the most common form of hypoadrenocorticism): decreased cortisol secretion from the adrenal cortex results in reduced negative feedback and increased release of ACTH. B: Secondary hypoadrenocorticism: lack of secretion of ACTH from the pituitary gland, leads to secondary atrophy of the adrenal cortex, specifically the zona fasciculata and zona reticularis.