Thu7October1249PM 3

A 17-year-old female presents with a two-day history of vomiting, general lethargy and giddiness.

Over the last six months, she had lost 5 kg in weight, had a reduced appetite and had been feeling increasingly lethargic. She had no past medical history of note, was a non-smoker and took the combined oral contraceptive pill for contraception. Her elder brother was well and there was a family history of thyroid disease with both her mother and maternal grandmother taking thyroxine.

On examination, she was comfortable at rest, appeared slightly dehydrated was apyrexial, had a body mass index of 18.5 kg/m2 and oxygen saturations on air of 99%. Her blood pressure was 102/64 mmHg and fell to 86/60 mmHg on standing. Her pulse was 90 beats per minute regular and auscultation of the heart and chest were normal. No abnormalities were detected on abdominal or CNS examination.

Investigations revealed:

Haemoglobin 105 g/L (115-165)

Mean cell volume 88 fL (80-96)

White cell count 8.8 ×109/L (4-11)

Neutrophils 4.4 ×109/L (1.5-7)

Lymphocytes 2.8 ×109/L (1.5-4)

Eosinophils 0.8 ×109/L (0.04-0.4)

Serum sodium 130 mmol/L (137-144)

Serum potassium 5.8 mmol/L (3.5-4.9)

Serum urea 12.8 mmol/L (2.5-7.5)

Serum creatinine 135 µmol/L (60-110)

Plasma glucose 3.8 mmol/L (3.0-6.0)

Free T4 8.8 pmol/L (10-22)

TSH 1.2 mu/L (0.4-5)

Urinalysis Ketones +

Which of the following is the most appropriate investigation for this patient?

(Please select 1 option)

Adrenal autoantibodies

Short Synacthen test This is the correct answer

MRI pituitary

CT adrenals Incorrect answer selected

Thyroid autoantibodies

Explanation

The salient features in this young patient's case are the longstanding asthenia with weight loss and the sudden episode of vomiting.

She appears clinically dehydrated as demonstrated by the postural hypotension but her results reveal a hyponatraemia, hyperkalaemia and hyperuricaemia. Her full blood count shows an eosinophilia.

The most likely diagnosis is acute hypoadrenalism due probably to Addison's disease in view of the strong family history of autoimmune disease. The diagnosis should be confirmed with a short Synacthen test and a cortisol response less than 550 nmol/L is confirmatory.

Abnormal thyroid function tests with low thyroxine (T4) and normal thyroid-stimulating hormone are quite commonly associated with Addison's and do not reflect secondary hypothyroidism but sick euthyroidism.

Thyroxine replacement must not be given to these patients as it can exacerbate the adrenal crisis. The thyroid function tests will normalise with hydrocortisone therapy.

Even if this were hypopituitarism an MRI of the pituitary would not diagnose hypoadrenalism and again this could be confirmed with a short Synacthen test.

Answer Statistics

1

4%

2

72%

3

11%

4

7%

5

9%

Times answered: 266