Acromegaly | |
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Lower jaw showing the classic spacing of teeth due to acromegaly. | |
Pronunciation | |
Specialty | Endocrinology |
Symptoms | Enlargement of the hands, feet, forehead, jaw, and nose, thicker skin, deepening of the voice [3] |
Complications | Type 2 diabetes, sleep apnea, high blood pressure, [3] high cholesterol, heart problems, particularly enlargement of the heart (cardiomegaly), osteoarthritis, spinal cord compression or fractures, increased risk of cancerous tumors, precancerous growths (polyps) on the lining of the colon. [4] |
Usual onset | Middle age [3] |
Causes | Excess growth hormone (hypersomatotropism) [3] |
Diagnostic method | Blood tests, medical imaging [3] |
Differential diagnosis | Pachydermoperiostosis [5] |
Treatment | Surgery, medications, radiation therapy [3] |
Medication | Somatostatin analogue, GH receptor antagonist [3] |
Prognosis | Usually normal (with treatment), 10 year shorter life expectancy (no treatment) [6] |
Frequency | 3 per 50,000 people [3] |
Acromegaly is a disorder that results in excess growth of certain parts of the human body. It is caused by excess growth hormone (GH) after the growth plates have closed. The initial symptom is typically enlargement of the hands and feet. [3] There may also be an enlargement of the forehead, jaw, and nose. Other symptoms may include joint pain, thicker skin, deepening of the voice, headaches, and problems with vision. [3] Complications of the disease may include type 2 diabetes, sleep apnea, and high blood pressure. [3]
Acromegaly is usually caused by the pituitary gland producing excess growth hormone. In more than 95% of cases, the excess production is due to a benign tumor, known as a pituitary adenoma. The condition is not inherited. Acromegaly is rarely due to a tumor in another part of the body. Diagnosis is by measuring growth hormone after a person has consumed a glucose solution, or by measuring insulin-like growth factor I in the blood. After diagnosis, medical imaging of the pituitary is carried out to determine if an adenoma is present. If excess growth hormone is produced during childhood, the result is the condition gigantism rather than acromegaly, and it is characterized by excessive height. [3]
Treatment options include surgery to remove the tumor, medications, and radiation therapy. Surgery is usually the preferred treatment; the smaller the tumor, the more likely surgery will be curative. If surgery is contraindicated or not curative, somatostatin analogues or GH receptor antagonists may be used. Radiation therapy may be used if neither surgery nor medications are completely effective. [3] Without treatment, life expectancy is reduced by 10 years; with treatment, life expectancy is not reduced. [6]
Acromegaly affects about 3 per 50,000 people. It is most commonly diagnosed in middle age. [3] Males and females are affected with equal frequency. [7] It was first described in the medical literature by Nicolas Saucerotte in 1772. [8] [9] The term is from the Greek ἄκρον (akron) meaning "extremity", and μέγα (mega) meaning "large". [3]
Features that may result from a high level of GH or expanding tumor include:[ citation needed ]
About 98% of cases of acromegaly are due to the overproduction of growth hormone by a benign tumor of the pituitary gland called an adenoma. [17] These tumors produce excessive growth hormone and compress surrounding brain tissues as they grow larger. In some cases, they may compress the optic nerves. Expansion of the tumor may cause headaches and visual disturbances. In addition, compression of the surrounding normal pituitary tissue can alter the production of other hormones, leading to changes in menstruation and breast discharge in women and impotence in men because of reduced testosterone production. [18]
A marked variation in rates of GH production and the aggressiveness of the tumor occurs. Some adenomas grow slowly and symptoms of GH excess are often not noticed for many years. Other adenomas grow rapidly and invade surrounding brain areas or the sinuses, which are located near the pituitary. In general, younger people tend to have more aggressive tumors. [19]
Most pituitary tumors arise spontaneously and are not genetically inherited. Many pituitary tumors arise from a genetic alteration in a single pituitary cell that leads to increased cell division and tumor formation. This genetic change, or mutation, is not present at birth but is acquired during life. The mutation occurs in a gene that regulates the transmission of chemical signals within pituitary cells; it permanently switches on the signal that tells the cell to divide and secrete growth hormones. The events within the cell that cause disordered pituitary cell growth and GH oversecretion currently are the subject of intensive research. [19]
Pituitary adenomas and diffuse somatomammotroph hyperplasia may result from somatic mutations activating GNAS, which may be acquired or associated with McCune–Albright syndrome. [20] [21]
In a few people, acromegaly is caused not by pituitary tumors, but by tumors of the pancreas, lungs, and adrenal glands. These tumors also lead to an excess of GH, either because they produce GH themselves or, more frequently, because they produce GHRH (growth hormone-releasing hormone), the hormone that stimulates the pituitary to make GH. In these people, the excess GHRH can be measured in the blood and establishes that the cause of the acromegaly is not due to a pituitary defect. When these nonpituitary tumors are surgically removed, GH levels fall and the symptoms of acromegaly improve.[ citation needed ]
In people with GHRH-producing, non-pituitary tumors, the pituitary still may be enlarged and may be mistaken for a tumor. Therefore, it is important that physicians carefully analyze all "pituitary tumors" removed from people with acromegaly to not overlook the possibility that a tumor elsewhere in the body is causing the disorder.[ citation needed ]
If acromegaly is suspected, medical laboratory investigations followed by medical imaging, if the lab tests are positive, confirm or rule out the presence of this condition.[ citation needed ]
IGF1 provides the most sensitive lab test for the diagnosis of acromegaly, and a GH suppression test following an oral glucose load, which is a very specific lab test, will confirm the diagnosis following a positive screening test for IGF1. A single value of the GH is not useful in view of its pulsatility (levels in the blood vary greatly even in healthy individuals).
GH levels taken 2 hours after a 75- or 100-gram glucose tolerance test are helpful in the diagnosis: GH levels are suppressed below 1 μg/L in normal people, and levels higher than this cutoff are confirmatory of acromegaly.[ citation needed ]
Other pituitary hormones must be assessed to address the secretory effects of the tumor, as well as the mass effect of the tumor on the normal pituitary gland. They include thyroid stimulating hormone (TSH), gonadotropic hormones (FSH, LH), adrenocorticotropic hormone, and prolactin.[ citation needed ]
An MRI of the brain focusing on the sella turcica after gadolinium administration allows for clear delineation of the pituitary and the hypothalamus and the location of the tumor. A number of other overgrowth syndromes can result in similar problems.[ citation needed ]
Pseudoacromegaly is a condition with the usual acromegaloid features but without an increase in growth hormone and IGF-1. It is frequently associated with insulin resistance. [22] Cases have been reported due to minoxidil at an unusually high dose. [23] It can also be caused by a selective post-receptor defect of insulin signalling, leading to the impairment of metabolic, but preservation of mitogenic, signaling. [24]
The goals of treatment are to reduce GH production to normal levels thereby reversing or ameliorating the signs and symptoms of acromegaly, to relieve the pressure that the growing pituitary tumor exerts on the surrounding brain areas, and to preserve normal pituitary function. Currently, treatment options include surgical removal of the tumor, drug therapy, and radiation therapy of the pituitary.[ citation needed ]
The primary current medical treatment of acromegaly is to use somatostatin analogues – octreotide (Sandostatin) or lanreotide (Somatuline). These somatostatin analogues are synthetic forms of a brain hormone, somatostatin, which stops GH production. The long-acting forms of these drugs must be injected every 2 to 4 weeks for effective treatment. Most people with acromegaly respond to this medication. In many people with acromegaly, GH levels fall within one hour and headaches improve within minutes after the injection. Octreotide and lanreotide are effective for long-term treatment. Octreotide and lanreotide have also been used successfully to treat people with acromegaly caused by non-pituitary tumors.[ citation needed ]
Somatostatin analogues are also sometimes used to shrink large tumors before surgery. [25]
Because octreotide inhibits gastrointestinal and pancreatic function, long-term use causes digestive problems such as loose stools, nausea, and gas in one-third of people. In addition, approximately 25 percent of people with acromegaly develop gallstones, which are usually asymptomatic. [26] In some cases, octreotide treatment can cause diabetes due to the fact that somatostatin and its analogues can inhibit the release of insulin.[ citation needed ] With an aggressive adenoma that is not able to be operated on, there may be a resistance to octreotide in which case a second-generation SSA, pasireotide, may be used for tumor control. However, insulin and glucose levels should be carefully monitored as pasireotide has been associated with hyperglycemia by reducing insulin secretion. [27]
For those who are unresponsive to somatostatin analogues, or for whom they are otherwise contraindicated, it is possible to treat using one of the dopamine agonists, bromocriptine, or cabergoline. As tablets rather than injections, they cost considerably less. These drugs can also be used as an adjunct to somatostatin analogue therapy. They are most effective in those whose pituitary tumours also secrete prolactin. Side effects of these dopamine agonists include gastrointestinal upset, nausea, vomiting, light-headedness when standing, and nasal congestion. These side effects can be reduced or eliminated if medication is started at a very low dose at bedtime, taken with food, and gradually increased to the full therapeutic dose. Bromocriptine lowers GH and IGF-1 levels and reduces tumor size in fewer than half of people with acromegaly. Some people report improvement in their symptoms although their GH and IGF-1 levels still are elevated.[ citation needed ]
The latest development in the medical treatment of acromegaly is the use of growth hormone receptor antagonists. The only available member of this family is pegvisomant (Somavert). By blocking the action of the endogenous growth hormone molecules, this compound is able to control the disease activity of acromegaly in virtually everyone with acromegaly. Pegvisomant has to be administered subcutaneously by daily injections. Combinations of long-acting somatostatin analogues and weekly injections of pegvisomant seem to be equally effective as daily injections of pegvisomant.[ citation needed ]
Surgical removal of the pituitary tumor is usually effective in lowering growth hormone levels. Two surgical procedures are available for use. The first is endonasal transsphenoidal surgery, which involves the surgeon reaching the pituitary through an incision in the nasal cavity wall. The wall is reached by passing through the nostrils with microsurgical instruments. The second method is transsphenoidal surgery during which an incision is made into the gum beneath the upper lip. Further incisions are made to cut through the septum to reach the nasal cavity, where the pituitary is located. Endonasal transsphenoidal surgery is a less invasive procedure with a shorter recovery time than the older method of transsphenoidal surgery, and the likelihood of removing the entire tumor is greater with reduced side effects. Consequently, endonasal transsphenoidal surgery is the more common surgical choice.[ citation needed ]
These procedures normally relieve the pressure on the surrounding brain regions and lead to a lowering of GH levels. Surgery is most successful in people with blood GH levels below 40 ng/ml before the operation and with pituitary tumors no larger than 10 mm in diameter. Success depends on the skill and experience of the surgeon. The success rate also depends on what level of GH is defined as a cure. The best measure of surgical success is the normalization of GH and IGF-1 levels. Ideally, GH should be less than 2 ng/ml after an oral glucose load. A review of GH levels in 1,360 people worldwide immediately after surgery revealed that 60% had random GH levels below 5 ng/ml. Complications of surgery may include cerebrospinal fluid leaks, meningitis, or damage to the surrounding normal pituitary tissue, requiring lifelong pituitary hormone replacement.[ citation needed ]
Even when surgery is successful and hormone levels return to normal, people must be carefully monitored for years for possible recurrence. More commonly, hormone levels may improve, but not return completely to normal. These people may then require additional treatment, usually with medications.[ citation needed ]
Radiation therapy has been used both as a primary treatment and combined with surgery or drugs. It is usually reserved for people who have tumours remaining after surgery. These people often also receive medication to lower GH levels. Radiation therapy is given in divided doses over four to six weeks. This treatment lowers GH levels by about 50 percent over 2 to 5 years. People monitored for more than 5 years show significant further improvement. Radiation therapy causes a gradual loss of production of other pituitary hormones with time. Loss of vision and brain injury, which have been reported, are very rare complications of radiation treatments.[ citation needed ]
The initial treatment chosen should be individualized depending on the person's characteristics, such as age and tumor size. If the tumor has not yet invaded surrounding brain tissues, removal of the pituitary adenoma by an experienced neurosurgeon is usually the first choice. After surgery, a person must be monitored long-term for increasing GH levels.[ citation needed ]
If surgery does not normalize hormone levels or a relapse occurs, a doctor will usually begin additional drug therapy. The current first choice is generally octreotide or lanreotide; however, bromocriptine and cabergoline are both cheaper and easier to administer. With all of these medications, long-term therapy is necessary, because their withdrawal can lead to rising GH levels and tumor re-expansion. [ citation needed ]
Radiation therapy is generally used for people whose tumors are not completely removed by surgery, for people who are not good candidates for surgery because of other health problems, and for people who do not respond adequately to surgery and medication.[ citation needed ]
Life expectancy of people with acromegaly is dependent on how early the disease is detected. [28] Life expectancy after the successful treatment of early disease is equal to that of the general population. [29] Acromegaly can often go on for years before diagnosis, resulting in poorer outcome, and it is suggested that the better the growth hormone is controlled, the better the outcome. [28] Upon successful surgical treatment, headaches and visual symptoms tend to resolve. [12] One exception is sleep apnea, which is present in around 70% of cases but does not tend to resolve with successful treatment of growth hormone level. [11] While hypertension is a complication of 40% of cases, it typically responds well to regular regimens of blood pressure medication. [11] Diabetes that occurs with acromegaly is treated with the typical medications, but successful lowering of growth hormone levels often alleviates symptoms of diabetes. [11] Hypogonadism without gonad destruction is reversible with treatment. [11] Acromegaly is associated with a slightly elevated risk of cancer. [30]
Cushing's syndrome is a collection of signs and symptoms due to prolonged exposure to glucocorticoids such as cortisol. Signs and symptoms may include high blood pressure, abdominal obesity but with thin arms and legs, reddish stretch marks, a round red face due to facial plethora, a fat lump between the shoulders, weak muscles, weak bones, acne, and fragile skin that heals poorly. Women may have more hair and irregular menstruation or loss of menses, with the exact mechanisms of why still unknown. Occasionally there may be changes in mood, headaches, and a chronic feeling of tiredness.
Growth hormone (GH) or somatotropin, also known as human growth hormone in its human form, is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals. It is thus important in human development. GH also stimulates production of insulin-like growth factor 1 (IGF-1) and increases the concentration of glucose and free fatty acids. It is a type of mitogen which is specific only to the receptors on certain types of cells. GH is a 191-amino acid, single-chain polypeptide that is synthesized, stored and secreted by somatotropic cells within the lateral wings of the anterior pituitary gland.
Gigantism, also known as giantism, is a condition characterized by excessive growth and height significantly above average. In humans, this condition is caused by over-production of growth hormone in childhood.
Hyperprolactinaemia is a condition characterized by abnormally high levels of prolactin in the blood. In women, normal prolactin levels average to about 13 ng/mL, while in men, they average 5 ng/mL. The upper normal limit of serum prolactin is typically between 15 to 25 ng/mL for both genders. Levels exceeding this range indicate hyperprolactinemia.
Cushing's disease is one cause of Cushing's syndrome characterised by increased secretion of adrenocorticotropic hormone (ACTH) from the anterior pituitary. This is most often as a result of a pituitary adenoma or due to excess production of hypothalamus CRH that stimulates the synthesis of cortisol by the adrenal glands. Pituitary adenomas are responsible for 80% of endogenous Cushing's syndrome, when excluding Cushing's syndrome from exogenously administered corticosteroids. The equine version of this disease is Pituitary pars intermedia dysfunction.
Somatostatin, also known as growth hormone-inhibiting hormone (GHIH) or by several other names, is a peptide hormone that regulates the endocrine system and affects neurotransmission and cell proliferation via interaction with G protein-coupled somatostatin receptors and inhibition of the release of numerous secondary hormones. Somatostatin inhibits insulin and glucagon secretion.
Growth hormone deficiency (GHD), or human growth hormone deficiency, is a medical condition resulting from not enough growth hormone (GH). Generally the most noticeable symptom is that an individual attains a short height. Newborns may also present low blood sugar or a small penis size. In adults there may be decreased muscle mass, high cholesterol levels, or poor bone density.
Insulin-like growth factor 1 (IGF-1), also called somatomedin C, is a hormone similar in molecular structure to insulin which plays an important role in childhood growth, and has anabolic effects in adults. In the 1950s IGF-1 was called "sulfation factor" because it stimulated sulfation of cartilage in vitro, and in the 1970s due to its effects it was termed "nonsuppressible insulin-like activity" (NSILA).
Hypopituitarism is the decreased (hypo) secretion of one or more of the eight hormones normally produced by the pituitary gland at the base of the brain. If there is decreased secretion of one specific pituitary hormone, the condition is known as selective hypopituitarism. If there is decreased secretion of most or all pituitary hormones, the term panhypopituitarism is used.
Pituitary adenomas are tumors that occur in the pituitary gland. Most pituitary tumors are benign, approximately 35% are invasive and just 0.1% to 0.2% are carcinomas. Pituitary adenomas represent from 10% to 25% of all intracranial neoplasms, with an estimated prevalence rate in the general population of approximately 17%.
A prolactinoma is a tumor (adenoma) of the pituitary gland that produces the hormone prolactin. It is the most common type of functioning pituitary tumor. Symptoms of prolactinoma are due to abnormally high levels of prolactin in the blood (hyperprolactinemia), or due to pressure of the tumor on surrounding brain tissue and/or the optic nerves. Based on its size, a prolactinoma may be classified as a microprolactinoma or a macroprolactinoma.
Octreotide, sold under the brand name Sandostatin among others, is an octapeptide that mimics natural somatostatin pharmacologically, though it is a more potent inhibitor of growth hormone, glucagon, and insulin than the natural hormone. It was first synthesized in 1979 and binds predominantly to the somatostatin receptors SSTR2 and SSTR5.
Multiple endocrine neoplasia type 1 (MEN-1) is one of a group of disorders, the multiple endocrine neoplasias, that affect the endocrine system through development of neoplastic lesions in pituitary, parathyroid gland and pancreas. Individuals suffering from this disorder are prone to developing multiple endocrine and nonendocrine tumors. It was first described by Paul Wermer in 1954.
A VIPoma or vipoma is a rare endocrine tumor that overproduces vasoactive intestinal peptide. The incidence is about 1 per 10,000,000 per year. VIPomas usually originate from the non-β islet cells of the pancreas. They are sometimes associated with multiple endocrine neoplasia type 1. Roughly 50–75% of VIPomas are malignant, but even when they are benign, they are problematic because they tend to cause a specific syndrome: the massive amounts of VIP cause a syndrome of profound and chronic watery diarrhea and resultant dehydration, hypokalemia, achlorhydria, acidosis, flushing and hypotension, hypercalcemia, and hyperglycemia. This syndrome is called Verner–Morrison syndrome (VMS), WDHA syndrome, or pancreatic cholera syndrome (PCS). The eponym reflects the physicians who first described the syndrome.
Nelson's syndrome is a disorder that occurs in about one in four patients who have had both adrenal glands removed to treat Cushing's disease. In patients with pre-existing adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas, loss of adrenal feedback following bilateral adrenalectomy can trigger the rapid growth of the tumor, leading to visual symptoms and hyperpigmentation. The severity of the disease is dependent upon the effect of ACTH release on the skin, pituitary hormone loss from mass compression, as well as invasion into surrounding structures around the pituitary gland.
Hyperpituitarism is a condition due to the primary hypersecretion of pituitary hormones; it typically results from a pituitary adenoma. In children with hyperpituitarism, disruption of growth regulation is rare, either because of hormone hypersecretion or because of manifestations caused by local compression of the adenoma.
Hypophysectomy is the surgical removal of the hypophysis. It is most commonly performed to treat tumors, especially craniopharyngioma tumors. Sometimes it is used to treat Cushing's syndrome due to pituitary adenoma or Simmond's disease It is also applied in neurosciences to understand the functioning of hypophysis. There are various ways a hypophysectomy can be carried out. These methods include transsphenoidal hypophysectomy, open craniotomy, and stereotactic radiosurgery.
Lanreotide, sold under the brand name Somatuline among others, is a medication used in the management of acromegaly and symptoms caused by neuroendocrine tumors, most notably carcinoid syndrome. It is a long-acting analogue of somatostatin, like octreotide.
Pegvisomant, sold under the brand name Somavert, is a growth hormone receptor antagonist used in the treatment of acromegaly. It is primarily used if the pituitary gland tumor causing the acromegaly cannot be controlled with surgery or radiation, and the use of somatostatin analogues is unsuccessful, but is also effective as a monotherapy. It is delivered as a powder that is mixed with water and injected under the skin.
Hypersomatotropism, also known as acromegaly, is an endocrine disorder caused by excessive growth hormone production in cats and dogs.