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Gigantism and Acromegaly: Differences and Similarities

Saima Andrabi   by Saima Andrabi, MS, Clinical Biochemistry    Last updated on January 28, 2020,

What Do Gigantism and Acromegaly Mean?

Both gigantism and acromegaly are hormonal disorder syndromes caused due to an over secretion of growth hormone, a condition called hypersomatotropism. Both these syndromes mostly occur due to a pituitary adenoma. Gigantism occurs before the closure of epiphyses and acromegaly occurs after the closure of epiphyses and result in various distinctive facial and other features.

Both these syndromes can be diagnosed by skull and hand x-rays and with measurement of growth hormone levels. Treatment options mainly involve removal or destruction of the responsible adenoma.

In most cases, it has been found that acromegaly and gigantism are secondary to a growth hormone secreting adenoma in the pituitary gland. Also, some secreations like growth hormone-releasing hormone (GHRH) released from a hypothalamic adenoma or ectopic GHRH released from lung or pancreas neuroendocrine tumors can result in acromegaly.

Acromegaly vs Gigantism: What Differentiates Gigantism From Acromegaly?

Both gigantism and acromegaly are birth defects and are very similar to each other; however the only difference is the period in which they occur. Gigantism usually occurs during childhood and acromegaly appears in adulthood. Acromegaly in adults occurs typically between the ages of 30 and 50. It occurs after the fusion of growth plate cartilage in adulthood. On the contrary, gigantism indicates abnormally high linear growth due to oversecretion of insulin like growth factor I (IGF-I). It occurs in childhood when the epiphyseal growth plates are open. Both these syndromes are rare conditions caused due to excessive secretion of growth hormone.

Genetics of Gigantism and Acromegaly

We are familiar now that gigantism and acromegaly are rare hormonal disorders caused due to an excessive growth hormone (GH) secretion. Gigantism occurs when excess GH causes increased linear growth prior to the end of puberty and epiphyseal closure. Most cases arise due to a benign GH-secreting pituitary adenoma.

Over the past two decades, it has been found that there are several genetic causes of pituitary gigantism and acromegaly including multiple endocrine neoplasia type 1 and 4, McCune-Albright syndrome, Carney complex, familial isolated pituitary adenoma, recently identified X-linked acrogigantism etc.

Demographics and Prognosis of Acromegaly and Gigantism

It has been found that 50 out of every 1 million people suffer from acromegaly. On the contrary, gigantism occurs even more rarely, with reported cases in the United States numbering only about 100 by the year 2004. Both these disorders affect males and females equally.

Untreated acromegaly is likely to cause early death in patients because of its effects on the heart, lungs, brain, or sometimes due to the development of cancer in the large intestine. If treated properly, patients with acromegaly may be able to live a normal lifespan.

Gigantism can decrease the life expectancy of patients especially in cases where the patients have uncontrollable GH levels, diabetes and heart diseases. However, under proper treatment, gigantic people can live a normal life span as well.

Prevention of Acromegaly and Gigantism by Removing Pituitary Gland


There are three important things that we should be aware of regarding our pituitary gland. It is buried away at the base of our brain, it is very important for us, and it is very prone to development of tumors. We all know that the pituitary gland is our master gland as it regulates the release of hormones from other glands of our body. It also helps us in controlling blood pressure, urine output, body temperature, growth, metabolism and various other functions.

Any tumor in our pituitary gland can be harmful and may impair our body functions. For example, if there is a tumor in the part of the pituitary gland that produces prolactin, it can result in irregular menstrual cycles or abnormal production of breast milk in females. Similarly, if the tumor grows from the part of the pituitary gland that is responsible for producing growth hormone, it can result in some rare conditions like gigantism in children and acromegaly in adults besides some other problems.

The symptoms of any abnormality caused due to pituitary tumors depend on the part of the pituitary gland where the tumor grows. This is actually the case with “functioning” tumors (tumors that secrete excess or little amount of a particular hormone). There are some other tumors called “non-functioning,” which do not secrete hormones at all. These tumors just take up space until they begin pressing on adjacent parts of the brain that doesn’t occur normally. Non-functioning tumors often present symptoms like headaches, vision loss, nausea, vomiting, or fatigue. Non-functioning tumors can sometimes result in a broad-based loss of pituitary function.

Pituitary tumors are very common. Almost 15 % of adults have at least one. However, some are asymptomatic and do not require any treatment. Others which produce symptoms need to be treated via medication, surgery, and radiation.

It has been suggested that removing a pituitary gland can prevent many hormonal disorders including gigantism and acromegaly. However, surgical removal of pituitary gland is very difficult and tricky. The reason is that pituitary gland is surrounded by very important structures like carotid arteries, optic nerves, the frontal lobes of the brain. Although it is very difficult to access or visualize the pituitary gland, surgeons are now able to remove pituitary tumors surgically in a safe and minimally invasive way with the help of several revolutionary technologies and modern expertise.

Why Do Gigantic or Giant People Die So Young?

It has been found that most folks with gigantism grow extremely tall, which can be a reason behind their early death. Tumors on the brain’s pituitary gland releases excess growth hormones and ultimately cause gigantism in children and acromegaly in adults. All of this extra height and growth hormone affects the heart in such people and is one of the most common causes of death in these patients due to heart failure. One of the reasons is that the heart has to stretch more to supply blood to such a huge person.

According to a review of growth hormone disorders, it has been suggested that the extra hormone production in people with gigantism can make their hearts thicker, but the blood-pumping chambers remain the same size. Over produced growth hormone also affect the body’s normal insulin function and therefore plenty of gigantic people who produce too much growth hormone suffer from diabetes.

Acromegaly Outlook Improves With Better Diagnostics and Treatment

Acromegaly is a rare, subtle disorder that until recently had a very high mortality rate almost twice that of the general population. Acromegaly can be treated as well as cured with the help of greater awareness, better therapeutics, and more precise imaging and biochemical assays. This way the mortality rate can be comparable to patients with a disease.

In the past majority of deaths from acromegaly were considered to be due to cardiovascular disease, but now cancer has taken the lead. Before fifty years, it was found that 50% of patients with acromegaly would die before 50 years of age, with 89% of them facing death before their 60’s.

Late Diagnosis is Common in Acromegaly

Commonly, the mean age of acromegaly onset is 32 years; however the disease is not usually diagnosed until years later - between ages 40 and 45 years. Acromegaly is a very rare disorder with an annual incidence of almost 3 to 4 cases per million people, which makes it difficult for clinicians to recognize and diagnose this disease.

In majority of the cases, acromegaly is caused due to a slow-growing pituitary benign tumor or adenoma which in turn causes excess growth hormone (GH) secretion, and thereby results in an elevated insulin-like growth factor-1 (IGF-1) level in the body. The pituitary tumor generally remains undetected until patients present symptoms like enlarged hands, feet, or soft tissues. Pituitary tumors are commonly imperceptible and this is the reason that most of them go undiagnosed.

The disease is difficult to diagnose in early stages and is most challenging because of its insidious nature. The reason behind this is that the condition usually involves normal GH concentrations, mild or absent clinical conditions, and a very small pituitary tumor, which is very difficult to be detected at an early stage by various magnetic resonance imaging techniques.

Ideally, acromegaly diagnosis is suspected when the growth hormone levels are greater than 0.4 μg/L and IGF-1 levels are increased. An oral glucose tolerance test showing growth hormone levels greater than 0.4 μg/L suggests acromegaly, which is then confirmed by magnetic resonance imaging of the pituitary gland.

Some common comorbidities, which make it difficult to diagnose acromegaly include cardiovascular disease, hypertension, sleep apnea, colon carcinoma, joint diseases, and thyroid cancer.