Question

A 60-year-old man suffered from 6 months of severe headaches and excessive perspiration, he also became aware that he had developed tunnel vision. He had a 12-yr history of hypertension and vague aches and pains in his shoulder and hand joints that were diagnosed as osteoarthrosis. On examination by his GP, he was found to have course facial features, a prominent jaw. He had bitemporal hemianopia, BP 145/105 mmHG and a slight glycosuria. He was sent for a lateral skull x-ray that showed an enlarged pituitary fossa. Blood tests showed: Fasting glucose 9.2 (Reference range 3.5-6.5 mmol/l) Luteinizing hormone 3.7 (Reference range 0.7-6.0 U/l) Follicle stimulating hormone 4.8 (Reference range <6 U/l) Prolactin 295 (Reference range <425 mU/l) Testosterone 18.1 (Reference range10-35 nmol/l) Growth hormone 8.0 (Reference range <10 mU/l) Cortisol (random) 458 (Reference range 250-700 nmol/l) TSH 3.2 (Reference range 0.3-6.0 mU/l) Free T4 15.6 (Reference range 9.4-25.0 pmol/l) What further biochemical tests would you perform?

Answer 1

Answer : Insulin-like growth factor-1 (IGF-1) and Oral glucose tolerance test (OGTT)

The clinical diagnosis is Acromegaly - which occurs due to over production of hormones from the pituitary gland.  

Points in favour of diagnosis

History of head ache; excessive sweating

Hypertension; Osteoarthritis

Coarse facial features; Prominent jaw (prognathism)

Visual field defects - Bitemporal hemianopia

Xray - enlarged pituitary fossa

" All these are features of acromegaly "

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Here in the above case, fasting glucose is high. All other hormones including growth hormone (GH) levels are normal. " Normal serum GH levels cannot rule out acromegaly, because the level of growth hormone fluctuates depending on the time of sample collection "

The biochemical tests to confirm the diagnosis are :  Insulin-like growth factor-1 (IGF-1) and Oral glucose tolerance test (OGTT) -gold standard test for acromegaly

Insulin-like growth factor-1 (IGF-1)

Growth hormone induces the generation of insulin-like growth factor 1. Elevated levels of IGF-1 usually indicate an increased production of GH.  IGF-1 levels reflects an average GH production, and do not vary depending on time of sample collection.

Oral glucose tolerance test (OGTT)

Here, the growth hormone levels are monitored after administration of 75 g oral glucose.

In normal individuals, a higher blood glucose level usually supresses growth hormone production. But in patients with acromegaly, the growth hormone levels remain elevated - which is diagnostic of Acromegaly.