Gigantism

What causes gigantism?

The etiology of gigantism may include infectious processes in the pituitary region or a pituitary adenoma with hyperplasia of eosinophilic cells.

The pathogenetic mechanism is associated with an excess of growth hormone (GH), which is an anabolic hormone. It stimulates the growth of all tissues by increasing the influx of amino acids into cells and enhancing protein synthesis.

• Insulin-like growth factor I (IGF-I, somatomedin) is produced in the liver under the action of GH. The GH and IGF-I complex stimulates bone tissue growth during adolescence.

Gigantism occurs in Beckwith-Wiedemann syndrome, which is characterized by macroglossia, gigantism, microcephaly, and visceromegaly; region 11p(15.5) is involved.

How does growth hormone affect metabolism?

The effect of GH on carbohydrate and fat metabolism is biphasic:

• Initial phase — insulin-like effect. The hormone increases glucose uptake by muscle and adipose tissue and inhibits lipolysis.
• Second phase — anti-insulin effects. GH inhibits glucose uptake and utilization, enhances lipolysis, increases glucagon production, and activates hepatic insulinase. Consequently, GH exerts a hyperglycemic effect.

Clinical presentation and complications

Accelerated growth lasts for several years. Over time, patients develop acromegaloid coarsening of facial features. In addition to tall stature, systemic disorders develop:

• Hypogenitalism — underdevelopment of internal and external genitalia due to decreased gonadotropic function of the pituitary gland. Primary amenorrhea or early cessation of menstruation is noted from the onset of the disease.
• Carbohydrate metabolism disorders — hyperglycemia, which frequently leads to the development of diabetes mellitus.
• Mental disorders — emotional instability, irritability, sleep disturbances, asthenia, and decreased mental performance. This is associated with impaired functions of cortical neurons and subcortical centers, a stress response to the disease, or concomitant hyperthyroidism.
• Somatic manifestations — muscle weakness, hypotonia, and hypotrophy.

How is the disease diagnosed and treated?

Diagnosis involves measuring height and comparing it with standard growth charts. The median (“0” line) reflects the statistical average ideal growth rate for a specific age and sex. A zone above +2 and +3 standard deviations indicates tall stature or gigantism and is an indication for in-depth examination.

For conservative treatment, synthetic hypothalamic hormone analogues are used. The key drug is octreotide (a somatostatin analogue). It suppresses growth hormone secretion.

Do not confuse: organ gigantism

In clinical terminology, the root mega- or megalo- is used to denote excessive enlargement of individual organs. For example, megacolon (megacolon) is gigantism of the colon, and megaduedenum is enlargement of the duodenum.

Class and exam questions

What else to study on this topic

• Growth Hormone (GH)
• Acromegaly
• Somatotropic pituitary adenoma
• Hyperpituitarism

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.