QuestionSBA
QuestionChoice
The likely underlying diagnosis is Addison’s disease. It is caused by autoimmune destruction of the adrenal cortex resulting in a decreased production of mineralocorticoids, glucocorticoids, and androgens. The main presenting features include lethargy, mood changes, anorexia, and hyperpigmentation. The diagnostic test is a short synacthen test. This involves measuring plasma cortisol before and after the administration of tetrosactide (an ACTH analogue). In Addison’s disease, there is a failure of exogenous ACTH to increase plasma cortisol - pointing to an adrenal cause. The presence of another autoimmune condition (coeliac disease) also makes the diagnosis of Addison’s more likely.
10006861
a
Short synacthen test
QuestionChoice
This is used to test for Cushing’s syndrome, which is caused by an increase in circulating glucocorticoids. In a healthy patient, cortisol production will be suppressed. However, in Cushing’s syndrome, there is a failure to suppress cortisol.
10006862
b
48-hour dexamethasone suppression test
QuestionChoice
These markers would be raised in a patient suffering from a pheochromocytoma.
10006864
d
Urinary catecholamines & metabolites
QuestionChoice
Thyroid function tests would be an important test to rule out the differential diagnosis of hypothyroidism. However, given the presentation of this patient, a diagnosis of Addison’s disease is more likely. Hypothyroidism is more likely to present with weight gain rather than weight loss.
10006865
e
Thyroid function tests
QuestionChoice
This is a test used to identify diabetes insipidus. It would not be of use in this patient.
10006863
c
Water deprivation test
Concept
Chapter
2693
3835
Adrenal insufficiency and Addison's Disease
Topic
133
Endocrinology
13919
A 34-year-old female attends her GP complaining of feeling more tired and weak than usual over the last few weeks. On further discussion, she mentions that she has lost weight recently and that her boyfriend has said she looks more tanned than usual despite spending less time outdoors. She has a past medical history of coeliac disease and does not smoke or drink alcohol. On examination, pigmentation is noted in the palmar creases and posterior neck. Blood tests are ordered which show a raised potassium and low sodium. Salivary cortisol is low.

What further investigation is most likely to be diagnostic for the likely underlying condition?
a