Acromegaly overview

# Overview
Acromegaly is a disease of excessive growth hormone secretion. The pituitary adenoma is the most common cause of acromegaly. Other causes of acromegaly include GHRH secreting tumors as hypothalamic tumors, small cell lung cancer, adrenal adenoma, and pheochromocytoma. Ectopic tumors as lymphoma and pancreatic islet cell tumor can cause acromegaly by secretion of GH. Pathogenesis of acromegaly depends on the hypersecretion of the growth hormone and insulin-like growth factor 1 (IGF-1). 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. 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. Common risk factors in the development of acromegaly are the risk factors for pituitary adenoma development. These risk factors include a family history of pituitary adenoma, McCune Albright syndrome, lung cancers and adrenal tumors. 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, and spinal cord compression. Common symptoms of acromegaly include enlarged hands and feet, headache, increase sweating, sexual dysfunction, skin thickening, deepening of the voice and, an enlarged tongue. An elevated concentration of serum growth hormone (GH) and insulin-like growth factor 1(IGF-1) levels is diagnostic of acromegaly. Endonasal transsphenoidal surgery is the mainstay of treatment for acromegaly due to pituitary adenoma. Patients with acromegaly are treated with somatostatin analogs like octreotide, dopamine agonists like bromocriptine, and GH receptor antagonist like pegvisomant. Radiation therapy is indicated in patients who do not respond to surgery or the medical therapy.

# 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 established system for the classification of 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 GHRH secreting 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 as Marfan 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, and spinal 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
On x-ray, acromegaly is characterized by widening of the joint spaces, soft tissue hypertrophy, and osteophyte formation.

## CT scan
There are no CT findings associated with acromegaly.

## MRI scan
Pituitary gland MRI may be helpful in the diagnosis of acromegaly as pituitary adenomas are the most common cause of acromegaly. Findings on MRI suggestive of acromegaly include enlarged pituitary gland and an adenoma that may extend to the suprasellar region. Spine MRI also may be helpful in the diagnosis as it shows hypertrophy of the spinal ligaments.

## 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.

# Treatment

## Medical Therapy
The mainstay of acromegaly treatment for is pharmacotherapy. Patients with acromegaly are treated with somatostatin analogs like octreotide, dopamine agonists like bromocriptine, and growth hormone receptor antagonist like pegvisomant. Radiation therapy is indicated in patients who do not respond to surgery or the medical therapy.

## Surgery
Surgery is the mainstay of treatment for acromegaly due to pituitary adenoma. The goal of the surgery will be the removal of the pituitary mass that causes acromegaly. The surgery to be performed is endonasal transsphenoidal surgery.

## Prevention
There are no established measures for the prevention of acromegaly.