Acromegaly overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Acromegaly (from Greek akros "extreme" or "extremities" and megalos "large" - extremities enlargement) is a hormonal disorder that results from too much growth hormone in the body. The pituitary gland, a small gland in the brain, makes growth hormone. In acromegaly, the pituitary produces excessive amounts of growth hormone, usually from a benign, or noncancerous, tumor on the pituitary gland. These benign tumors are called pituitary adenomas.
Acromegaly most commonly affects middle-aged adults and can result in serious illness and premature death. Because of its insidious onset and slow progression, the disease is hard to diagnose in the early stages and is frequently missed for many years. Common symptoms include slow enlargement of jaw, hands, feet, and coarsening of facial features. The most serious health consequences of acromegaly are type 2 diabetes, high blood pressure, increased risk of cardiovascular disease, and arthritis. Patients with acromegaly are also at increased risk for colon polyps, which may develop into colon cancer if not removed.
When growth hormone-producing adenomas occur in childhood, the disease that results is called gigantism rather than acromegaly. A child’s height is determined by the length of the so-called long bones in the legs. In response to growth hormone, these bones grow in length at the growth plates—areas near either end of the bone. Prior to puberty, excessive growth hormone exposure causes increased height. Growth plates fuse after puberty, so the excessive growth hormone production in adults does not affect height.
Historical Perspective
Acromegaly was first described by DR. Johannes Wier in 1567. Dr. Verga reported a case of acromegaly in 1864 and it was a case of a patient with a disproportionate big face. Through 1877 to 1900s, many physicians reported cases of acromegaly. In 1970, Dr. Besser used bromocriptine in the treatment of acromegaly and it showed a remarkable improvement in the patients. In 1988, FDA approved for the octreotide as a treatment to acromegaly.
Classification
There is no classification system established for acromegaly
Pathophysiology
Acromegaly pathogenesis depends mainly on the excessive secretion of the growth hormone from the pituitary gland. Pituitary somatotroph cell adenoma leads to hypersecretion of the growth hormone. Insulin-like growth factor 1 (IGF-1) inhibits the secretion of growth hormone in two ways. IGF-1 inhibits directly the somatotroph cells or stimulates secretion the somatostatin that inhibits the GH secretion. The IGF-1 is responsible for the acral features of the acromegaly. The IGF-1 causes the rapid increase in the hand and feet size, forehead protrusion, and jaw prominence. A genetic mutation in the alpha subunit of the guanine nucleotide stimulatory protein leads to increase synthesis of cAMP which increases the secretion of growth hormone. Acromegaly is associated with Multiple Endocrine Neoplasia 1 (MEN-1), Carney complex, McCune-Albright syndrome, paraganglioma, and pheochromocytoma.
Causes
Common causes of acromegaly include pituitary adenoma and acidophil stem cell adenomas. Less common causes of acromegaly include GHRHsecreting tumors as hypothalamic tumors, small cell lung cancer, adrenal adenoma, and pheochromocytoma. Other causes include GH secreting tumors as lymphoma and pancreatic islet cell tumor.
Differentiating Acromegaly overview from Other Diseases
Acromegaly must be differentiated from other diseases that cause acral features like skin thickening and linear bone growth. These diseases such asMarfan syndrome, precocious puberty, prolactinoma, and pachydermoperiostosis.
Epidemiology and Demographics
The prevalence of acromegaly is estimated to be 2.8 - 13.7 per 100.000 individuals worldwide. In the United States, the incidence of acromegaly is 0.11 per 100,000 individuals. Acromegaly affects men and women equally.
Risk Factors
Common risk factors in the development of acromegaly are the risk factors for pituitary adenoma development. These risk factors include a family history ofpituitary adenoma, MacCun Albright syndrome, lung cancers and adrenal tumors. Other risk factors include early menopause in females and young age females at the first childbirth.
Screening
According to the endocrine society, screening for acromegaly is recommended among patients with clinical features of acromegaly. These features include enlarged hands and feet, frontal protrusion, and skin thickening. The screening is performed by measurement of the IGF-1.
Natural History, Complications, and Prognosis
If left untreated, 30% of patients with acromegaly may progress to develop cardiovascular manifestations, pulmonary dysfunction, and cerebral complications. Common complications of acromegaly include hypertension, arrhythmia, heart failure, sleep apnea, dyspnea, carpal tunnel syndrome, andspinal cord compression. Prognosis of acromegaly is generally good with transsphenoidal surgery and the postoperative treatment.
Diagnosis
History and Symptoms
Common symptoms of acromegaly include enlarged hands and feet, headache, increase sweating, sexual dysfunction, skin thickening, deepening of the voice and, an enlarged tongue. Less common symptoms of acromegaly include visual defects and irregular menses in the women.
Physical Examination
Patients with acromegaly usually appear tired. Physical examination of patients with acromegaly is usually remarkable for skin tags, acanthosis nigricans, and hyperhidrosis. Common findings in physical examination include frontal bossing, headache, macroglossia, and prognathism. Cardiovascular findings include ventricular hypertrophy, heart failure, and arrhythmias. Skeletal findings include joint effusion, osteopenia, kyphoscoliosis, muscle weakness, paraesthesia, and malocclusion of the mouth leading temporomandibular joint tenderness.
Laboratory Findings
An elevated concentration of serum growth hormone (GH) and insulin-like growth factor 1(IGF-1) levels is diagnostic of acromegaly.
X ray
CT scan
There are no CT findings associated with acromegaly.
MRI scan
Ultrasound
There are no ultrasound findings associated with acromegaly.
Other Diagnostic Studies
There are no other diagnostic studies associated with acromegaly.
Other imaging findings
There are no other imaging findings associated with acromegaly.