Corticotrophin Deficiency

Corticotrophin is one of the last of the adenohypophysial hormones to be impaired in pituitary damage. The clinical signs of a patient with corticotrophin deficiency are similar to those of a patient with primary adrenocorticoid deficiency (see adrenals). The most common presenting symptom will be general fatigue. The major differences between corticotrophin deficiency and primary adrenocorticoid deficiency are:

• In primary adrenocorticoid deficiency there are raised levels of ACTH and the skin will be pigmented (see adrenal section). The raised levels of ACTH are not found in corticotrophin deficiency
• Dehydration is a major symptom of primary adrenocortocoid deficiency as there is a loss of mineralocorticoid activity. This activity is not lost in corticotrophin deficiency.

Diagnosis

The diagnosis of corticotrophin (ACTH) deficiency is difficult as the current plasma ACTH assays are not sensitive enough to distinguish between normal and low levels. The synacthen test (synthetic ACTH) is also associated with problems as unstimulated adrenal glands (in corticotrophin deficiency) will atrophy and will not respond. Other tests can be used which normally stimulate corticotrophin release, for example, metyrapone (11-hydroxylase inhibitor in cortisol synthesis) will reduce cortisol levels and stimulate the release of ACTH in the normal subject.

Treatment

The standard treatment for a patient with corticotrophin deficiency is the administration of glucocorticoids. The glucocorticoids are replaced by oral hydrocortisone (20-30mg daily). It is important to remember that this regimen is increased in times of stress (i.e. illness).