Acromegaly
Study guide:
Definition:
Acromegaly is broadening of the skeleton that occurs as a result of hypersecretion of the pituitary growth hormone (GH).It produces Gigantism (if acquired before epiphyseal closure) in children, and acromegaly (if acquired after epiphyseal closure) in adults.
Pathopyhsiology:
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Excess growth hormone stimulates the proliferation of bones, cartilages, tissues leading to organomegaly.
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In normal situations, GH acts as a catabolic hormone to increase blood glucose levels, in cases of excess GH, there is loss of hypoglycemic stimulation and glucose suppression.
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Insulin resistance and impaired glucose tolerance.
Etiology:
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Acromegaly usually occurs sporadically, although gene mutations can rarely give rise to familial acromegaly, typically the AIP gene in familial isolated pituitary adenoma.
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Commonly, it is cause by a GH-secreting pituitary adenoma (10% of pituitary adenomas)
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Other causes are:carcinoidor pancreatic islet tumourssecretingectopic GHRH resulting in excess GH.
Diagnosis:
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Elevated serum insulin like growth factor-1(IGF-1, also known as somatomedin C) — is the first line diagnostic test.
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Oral glucose suppression test (most specific) — 75 g of glucose PO suppress GH levels in healthy individuals but not in patients with acromegaly.
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MRI of the pituitary— to look for tumors.
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CT, MRI, or skull X-raysmay show cortical thickening, enlargement of the frontal sinuses, and enlargement and erosion of the Sella turcica.
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Visual field examination: defects are common (bitemporal hemianopsia)
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Pituitary function:partial or complete anterior hypopituitarism is common.
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Prolactin: mild to moderate hyperprolactinemia occurs in 30% of patients.
Management:
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Untreated acromegaly results in reduced survival.
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Most deaths occur from heart failure, coronary artery disease and hypertension-related causes.
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When present, hypopituitarism should be corrected and concurrent diabetes and/or hypertension should be treated conventionally; both usually improve with treatment of the acromegaly.
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The aim of therapy is to achieve a mean growth hormone level below 2.5 μg/L.
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Surgery:Trans-sphenoidal surgery is the appropriate first-line therapy.
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Pituitary radiotherapy: if IGF-1 levels stay elevated after surgery.
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Medical therapy: There are three receptor targets to suppress GH secretion for the treatment of acromegaly:
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Somatostatin receptor agonists: Octreotide and lanreotide
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Dopamine agonists:bromocriptinean cabergoline— can be given to shrink tumours prior to definitive therapy or to control symptoms and persisting GH secretion.
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Growth hormone antagonists: Pegvisomant

References:
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Kumar and Clark’s Clinical Medicine, 8th ed.
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Step Up to Medicine 4th Edition.
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Toronto Notes 2017
First author: Fai Alhoshan
Format Editor: Adel Yasky
Bayan Alzomaili