Lack of ACTH secretion produces the symptoms of hypoadrenalism, particularly weakness and tiredness, nausea and vomiting, and progression to dizziness on standing due to postural hypotension. ACTH deficiency results in reduced adrenal androgen secretion and contributes to the decreased libido and loss of secondary sexual hair seen in hypopituitarism. In pituitary ACTH deficiency, there is also pallor of the skin (Fig. 2.15). Hypoglycaemia can occur in hypoadrenalism for two reasons: first, because of increased insulin sensitivity due to a lack of cortisol (cortisol is an insulin antagonist), and, second, because adrenal insufficiency decreases hepatic glycogen reserves.
