Acromegalia y gigantismo

Classification of hyperpituitarism and pathogenesis mechanisms

Globally, hyperpituitarism is divided into partial and total. The total form is extremely rare and its existence is questionable. Partial forms of hyperpituitarism include a spectrum of endocrine disorders:

1. Pituitary gigantism.
2. Acromegaly.
3. Hyperprolactinemia.
4. Hypermelanotropinemia.
5. Pituitary (true) precocious puberty syndrome.
6. Pituitary hyperthyroidism.
7. Pituitary hypercorticism (Cushing's disease).

The development of gigantism and acromegaly is associated with disorders at different levels of regulation. There are three key forms of pathogenesis (initial links):

• Centrogenic mechanism. Occurs as a result of damage to neurons of the cerebral cortex and/or hypothalamus. This leads to massive hyperproduction of somatoliberin and growth hormone (GH) itself. In some cases, the triggering factor is a decrease in the normal production of somatostatin, which normally inhibits GH secretion.
• Primary glandular (pituitary) mechanism. Is a direct consequence of increased GH synthesis directly by acidophilic cells of the adenohypophysis.
• Post-glandular (receptor) mechanism. In this case, hormone levels may not be critically high, but there is increased hyperaffinity (pathological affinity) of receptors in target tissues and organs for GH molecules.

Clinical manifestations of gigantism

Gigantism is characterized by large-scale systemic alterations that affect not only appearance but also internal systems.

Skeletal and organ changes The leading symptom is height growth above the physiological norm (more than 200 cm in young men and 190 cm in young women). The basis is accelerated epiphyseal and periosteal growth of tubular bones. There is often a mismatch between the size of internal organs and body parameters. As a rule, splanchnomegaly (enlargement of organs) develops, but in rare cases, internal organs may relatively lag behind in growth. In both scenarios, this leads to functional insufficiency of, for example, the heart or liver, as their capacities do not match the increased load of a massive body.

Muscular and reproductive systems Muscle development occurs disproportionately. At the beginning of the disease, muscle mass still corresponds to overall body dimensions. However, as it progresses, muscle growth begins to critically lag behind. Degenerative changes start in myofibrils, and muscle tissue is replaced by connective tissue, which clinically manifests as hypotonia, hypotrophy, and pronounced muscle weakness. Concurrently, hypogenitalism (underdevelopment of internal and external genitalia) develops, caused by insufficient synthesis or effects of gonadotropins.

Metabolism and psyche Since GH is a potent counter-regulatory hormone, patients naturally experience impaired carbohydrate metabolism: hyperglycemia is recorded, and diabetes mellitus frequently manifests. The mental status of patients is characterized by emotional instability, irritability, sleep disturbances, asthenia, and decreased mental performance. This is associated with the dysfunction of cortical and subcortical neurons, the stress response to a severe illness, and concomitant hyperthyroidism.

Specifics of the clinical picture of acromegaly

While gigantism occurs during active ontogenesis, acromegaly has its own course features associated with the effects of excess GH on an already formed organism.

Musculoskeletal system and soft tissues Characterized by enlargement of the hands and feet due to somatotropin-stimulated periosteal bone growth. Soft tissues become dense, skin thickens, and facial features become coarse. Macroglossia (enlargement of the tongue) and splanchnomegaly are observed. These changes are the result of excessive proliferation of connective tissue and parenchymal elements under the direct influence of GH.

Neurological and mental symptoms Due to bone thickening and soft tissue hypertrophy, bone canals and depressions narrow. This leads to compression of the nerve trunks passing there. Clinically, this is expressed as paresthesias, especially acroparesthesias (pronounced discomfort, numbness, and tingling in the hands and feet). Various mental disorders are also recorded.

Metabolism and reproductive function

• Carbohydrate metabolism: persistent hyperglycemia is noted (in more than 50% of patients), and every tenth patient develops full-blown diabetes mellitus.
• Lipid metabolism: the blood concentration of cholesterol, lecithin, free fatty acids (FFAs), ketone bodies (KBs), and lipoproteins (LPs) increases.
• Reproductive sphere: excessive GH effects provoke a decrease in libido, impotence, and in women — dysmenorrhea and galactorhea.

Preguntas de clases y exámenes

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• Mechanisms of development of pituitary hypercorticism (Cushing's disease)
• Pathogenesis and clinical picture of pituitary hyperthyroidism
• Pituitary precocious puberty syndrome: differential diagnosis
• Detailed changes in the lipid profile in hyperpituitarism
• Interaction of GH and gonadotropins in the development of hypogenitalism

Otros temas de la sección «Capítulo 27. Formas típicas de la patología del sistema endocrino»

Material preparado por los profesores de WhiteCoat Pro según el plan de estudios de las facultades de medicina. De carácter educativo.