1. Acromegaly
Growth hormone stimulates the production of insulin-like growth factor-I (IGF-I), which is produced
in the liver and many other tissues. IGF-I is the main mediator of the actions of growth hormone.
 Acromegaly is usually caused by excessive secretion of growth hormone by a pituitary
macroadenoma or microadenoma.
 Other rare causes include increased growth hormone-releasing hormone (GHRH) from
hypothalamic tumours, and ectopic GHRH or growth hormone from non-endocrine tumours,
e.g. lung cancer, cancer of the pancreas, carcinoid, medullary carcinoma of the thyroid.
Acromegaly causes an overgrowth of all organ systems, bones, joints and soft tissues.
Epidemiology
 Incidence is 3-4 per million subjects per year.1
 Acromegaly most often occurs in adults aged 30-50 years.
Presentation
Often an insidious onset and symptoms may precede the diagnosis by several years.
 Due to tumour:
o Headaches.
o Visual field defects: the most common defect is a bitemporal hemianopia.
 Due to excess of growth hormone:
o Gradual change in appearance due to the effects on cartilage and soft tissues:
enlargement of hands and feet (increase in ring and shoe size), frontal bossing,
thickening of the nose, enlarged tongue (macroglossia), growth of the jaw
(prognathism), and coarsening of facial features.
o Macroglossia may cause obstructive sleep apnoea leading to daytime tiredness.
o Excessive sweating and oily skin, with development of skin tags. Women may have
mild hirsutism.
o Articular overgrowth of synovial tissue and arthropathy leading to arthritis
(widespread osteoarthritis of the weight-bearing joints), back pain and kyphosis.
o Visceral hypertrophy, e.g. heart, liver, thyroid (with a multinodular goitre), prostate
and kidneys.
o Nerve compression symptoms may occur, especially carpal tunnel syndrome.
o Cardiac features include hypertension, left ventricular hypertrophy,
cardiomyopathy and arrhythmias.
 Due to associated hyperprolactinaemia, e.g. galactorrhoea, amenorrhoea.
 Hypopituitarism: decreased secretion of anterior pituitary hormones and compression of
pituitary stalk.

2. Investigations
 Visual field tests.
 Blood glucose; serum phosphate, urinary calcium and serum triglycerides may also be
raised.
 Assessment of growth hormone:
o Random growth hormone: often not diagnostic because of episodic secretion and
short half-life of the hormone.
o Glucose tolerance test: growth hormone is normally inhibited by glucose. The
diagnosis of acromegaly can be confirmed by documenting an elevated insulin-like
growth factor-I (IGF-I) level in combination with failure of growth hormone to
suppress after oral glucose to below 0.3 micrograms per litre, when growth hormone
is measured with a highly sensitive and specific assay.2
o IGF-I: long half-life and so is a useful measurement to assess growth hormone
secretion and therefore screen for acromegaly and monitor the effect of therapy.3
o IGF-binding protein-3 (IGFBP-3): is the main binding protein for circulating IGF and is
increased in acromegaly. Can be useful in the diagnosis of acromegaly.
o Growth hormone-releasing hormone (GHRH) concentration can be obtained if
clinically indicated.
 Assessment of other pituitary hormones: prolactin, adrenal, thyroid, and gonadal hormones.
 MRI scan of pituitary and hypothalamus: more sensitive than CT scan.
 CT scan: for lung, pancreatic, adrenal or ovarian tumours that may secrete ectopic growth
hormone or GHRH.
 Total body scintigraphy with radio-labelled octreoscan (somatostatin) to aid localisation of
the tumour.
 Cardiac assessment: electrocardiogram, echocardiogram.
Screening for colorectal cancer
Because patients with acromegaly have an increased prevalence of colorectal adenomas and
cancer, it is recommended that patients with acromegaly should be offered regular colonoscopy
screening, starting at the age of 40 years.
Differential diagnosis
Pseudoacromegaly is the presence of a similar physical appearance in the absence of elevated
growth hormone or insulin-like growth factor-I (IGF-I). Causes of pseudoacromegaly include insulin
resistance associated with hyperinsulinaemia,5
and minoxidil treatment.6
Management
The aim of management is to control the symptoms caused by the local effects of the tumour and
due to the excess hormone production, and to normalise hormone levels. No single treatment is
completely effective in achieving these aims and so a combination of treatments is required,
usually with surgery as first line treatment and drug treatment for residual disease.7
 Trans-sphenoidal surgery is the treatment of choice in most cases. Remission rates are 80-
85% for microadenomas and 50-65% for macroadenomas.8
Patients with residual disease can
then be offered adjuvant treatment.
 Patients may need drug treatment after surgery to reduce growth hormone levels.
 Radiotherapy is used for refractory disease, as an adjuvant for large invasive tumours and
when surgery is contra-indicated.

3. Drug treatment
 Somatostatin analogues:
o Octreotide and lanreotide are analogues of the hypothalamic release-inhibiting
hormone somatostatin.
o Growth hormone-secreting pituitary tumours can expand during treatment and
patients should therefore be monitored for signs of tumour expansion, e.g.
regular assessment of visual fields.
 Dopamine agonists: bromocriptine and cabergoline are effective but are less effective
than somatostatin analogues.10
Tumours that also secrete prolactin have a better
response rate to dopamine agonists.
 Pegvisomant:
o Genetically modified analogue of human growth hormone and is highly selective
growth hormone receptor antagonist.
o Has been shown to normalise insulin-like growth factor-I (IGF-I) levels in 90-100% of
patients.
o Growth hormone levels increase during treatment and no decrease in tumour size is
seen.
o Pegvisomant is licensed for the treatment of acromegaly in patients with
inadequate response to surgery, radiotherapy or somatostatin analogues.
Complications
Complications of acromegaly include:
o Ischaemic heart disease, cardiac failure, cerebrovascular disease.
o Diabetes.
o Acromegalic arthropathy affects up to 70% of patients and involves both the axial and
peripheral skeleton.1
o Obstructive sleep apnoea.
o Increased incidence of colonic polyps and adenocarcinoma
of the colon.
 Patients may develop hypopituitarism immediately after surgery, or several years after
radiotherapy.
 Damage caused by the tumour may result in hyperprolactinaemia and deficiencies of
glucocorticoids, sex steroids and thyroid hormone.
Prognosis
 High levels of growth hormone, even when the patient has no symptoms, are associated
with a 2 to 3-fold increase in mortality.11
 Tumour size: microadenoma (tumour less than 10 mm) is associated with a better prognosis
than macroadenoma, mainly because persistence of disease after surgery is more common
with macroadenomas.
 Reduction of growth hormone response to a glucose load is the most important factor in
increasing survival. Raised growth hormone levels following treatment are associated with
significantly increased mortality rates.
 Hypertension, cardiovascular disease and diabetes are poor prognostic factors.
 Long duration of symptoms is also a poor prognostic factor.