Gigantism vs Acromegaly

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Illustration of tow mans one who has Acromegaly and the other has gigantism

Introduction

Gigantism and acromegaly are both conditions that are brought about by an overproduction of growth hormone resulting in excessive growth which is almost always due to a benign pituitary adenoma or tumor. This excessive growth condition is called gigantism when the condition occurs during childhood while it is called acromegaly when the condition occurs during adulthood.

Causes

Gigantism is the abnormally high linear growth caused by the excessive action of insulin growth factor 1 (IGF-1) while the epiphyses are open during childhood. Acromegaly is the abnormally high linear growth also caused by the excessive action of IGF-1 that occurs after the epiphyseal growth plate closes in adulthood.

The anterior lobe of the pituitary gland is the one responsible for producing growth hormones. The growth hormone triggers the growth of muscles, bones, and other internal organs. An excessive growth hormone results in an abnormally booming growth of these tissues. Aside from a noncancerous pituitary tumor that usually causes the overproduction of the growth hormone, there are also certain rare lung and pancreas tumors that have the ability to produce hormones that trigger the pituitary gland to produce excessive amounts of growth hormone.

Other Causes

  • Neurofibromatosis
  • Carney complex
  • Multiple endocrine neoplasia types 1 (MEN-1)
  • McCune-Albright syndrome (MAS)

Symptoms of Gigantism

The onset of the symptoms of gigantism is usually dramatic. These are the following symptoms of gigantism:

  • Tall stature
  • Enormous growth of long bones
  • Lengthening of the arms and legs
  • Mild to moderate obesity
  • Headaches
  • Larger head circumference of more than 2 standard deviations above the mean value for a specific gender or age also known as macrocephaly
  • Soft-tissue swelling
  • Soft tissue hypertrophy
  • Enlarged peripheral nerves
  • Visual changes
  • Pituitary insufficiency or hypopituitarism where the pituitary gland does not produce enough of certain hormones or fails to produce one or more of its hormones
  • Exaggerated growth of the hands with thick fingers
  • Exaggerated growth of the feet with thick toes
  • Rough facial features
  • Frontal bossing – a prominent protruding forehead which can be associated with a heavier brow ridge
  • Excessive sweating or hyperhidrosis
  • Prognathism – protrusion of the upper jaw (maxilla) or lower jaw (mandible) beyond a predetermined imaginary line in the coronal plane of the skull
  • Delayed puberty
  • Hypogonadotropic hypogonadism – diminished functional activity of the reproductive glands that can cause a decline in sex hormone biosynthesis or an interrupted stage of puberty
  • Peripheral neuropathies such as carpal tunnel syndrome
  • Eunuchoid habitus – a body habitus that is tall, underweight, and slim with long arms and long legs
  • Cardiovascular disease
  • Osteoarthritis
  • Endocrinopathies or hormonal problems
  • Benign tumors

Symptoms of Acromegaly

The onset of the symptoms of acromegaly in adults is usually subtle. These are the following symptoms of acromegaly:

  • Coarsening of facial features
  • Doughy-feeling skin over the face and extremities
  • Soft-tissue swelling of the feet and hands
  • Noticeably large pores
  • Thickening and darkening of the skin
  • Headaches
  • Nasal bone hypertrophy
  • Enlargement of the lower lip
  • Enlarged and furrowed tongue
  • Deepening of the creases on the nasolabial folds and forehead
  • Increase in coarse body hair
  • Hard and thick nails
  • Thick and edematous eyelids
  • Oily skin
  • Wide spacing of the teeth
  • Frontal Bossing
  • High blood pressure
  • Increase in the size and function of the sweat and sebaceous glands
  • Excessive apocrine and eccrine sweating
  • Offensive body odor
  • Cartilaginous proliferation of the larynx that causes the patient to have a deep husky voice
  • Prognathism
  • Excessive hair growth all over the body or hypertrichosis
  • Peripheral neuropathies
  • Sleep apnea
  • Cutis verticis gyrata – excessive formation of scalp skin that creates deep folds on the scalp
  • Mitral valvular regurgitation – a condition where the heart’s mitral valve does not close tightly letting blood leak backward into the heart interrupting the flow of the blood to the rest of the body or through the heart
  • Milky nipple discharge or galactorrhea in women
  • Shrinking of the breasts in women
  • Mild hirsutism, a condition of male-pattern hair growth in women
  • Costal cartilage growth that results in a barrel chest
  • Articular cartilaginous proliferation
  • Impaired glucose tolerance in 50% of patients
  • Hyperpigmentation in 40% of patients
  • Cardiac disease in 30% of patients
  • Diabetes mellitus in 10% of patients

Diagnosis

Gigantism and acromegaly can be diagnosed through the following procedures:

  1. Blood tests confirm the diagnosis of both conditions when they show high levels of the growth hormone and insulin-like growth factor 1 (IGF-1).
  2. Oral glucose tolerance test is performed by giving the patient a glucose drink to suppress the growth hormone levels and show that normal suppression doesn’t occur.
  3. MRI or CT Scan is done to detect abnormal growths in the pituitary gland. MRI can show images of pituitary adenomas while CT scan can show ovarian, pancreatic, and adrenal tumors secreting growth hormones.
  4. Radiography is done to demonstrate skeletal manifestations of the excess GH or IGF-1

Treatment

There is no single procedure that can achieve control over an excess of the growth hormone. Doctors usually recommend a combination of these treatments to cure gigantism and acromegaly:

  • Surgery

Transsphenoidal surgery is regarded as the first line of treatment to remove a pituitary tumor if it is the one causing the excessive growth. This reduces the size of the tumor and the production of the growth hormone without causing a deficiency of other pituitary hormones.

If surgery alone is not enough to cure the condition because the tumor is already large by the time it is found, radiation therapy is used as a follow-up treatment especially when a substantial amount of tumor remains and hypersecretion of growth hormone still can’t be controlled after surgery.

  • Radiation therapy

This treatment uses supervoltage irradiation but it may take several years for the growth hormone levels to drop and go back to normal and it may affect normal tissues and cause deficiencies in other pituitary hormones. Stereotactic radiosurgery speeds up the results and spares the normal pituitary tissue. Heavy particle radiation which is only available in a few centers, permits the delivery of larger doses of radiation to the pituitary but poses a higher risk of hypothalamic and cranial nerve damage.

  • Drugs

Medications can be taken to reduce growth hormone levels, prevent growth in stature, and block the effects of growth hormone:

  1. Somatostatin analogs such as octreotide and lanreotide suppress growth hormone secretion effectively.
  2. Dopamine-receptor agonists like cabergoline and bromocriptine mesylate are used as additional treatments to reduce the release of growth hormone but are less effective.
  3. Pegvisomant is a growth hormone receptor blocker that reduces or blocks the effects of growth hormone and lowers IGF-1 levels.