Pituitary gland pathology includes conditions characterized by an excess or deficiency of its hormones. These disorders are driven by neoplasms, tissue necrosis, genetic defects, and autoimmune processes, leading to severe endocrine disturbances.
Frequency of adenomasPituitary adenomas account for about 10% of all intracranial tumors
ProlactinomaThe most frequent adenoma, occurring 6 times less frequently in men than in women
PanhypopituitarismSimmonds syndrome occurs when more than 90% of anterior lobe cells are destroyed
Sheehan syndromePituitary necrosis due to severe hemorrhage during or after childbirth
Hypopituitarism (Pituitary Insufficiency)
Develops upon destruction or compression of adenohypophyseal tissue. Main forms include:
Postpartum necrosis (Sheehan syndrome). Caused by blood flow disruption during massive blood loss in childbirth. Due to the absence of the blood-brain barrier in the pituitary gland, abnormal proteins enter the bloodstream, triggering low-grade autoimmune inflammation.
Pituitary cachexia (Simmonds syndrome). An acute condition against the background of sepsis, trauma, or tumors, in which over 90% of secreting cells are destroyed. Deficiency of all tropic hormones (panhypopituitarism) leads to rapid weight loss (20–25 kg in the first month).
Empty sella syndrome. A pathology associated with a defect in the sellar diaphragm. Cerebrospinal fluid pressure causes atrophy and sclerosis of the gland.
Suprasellar tumors. The most well-known is craniopharyngioma (arising from Rathke's pouch remnants). In children, it causes growth and pubertal retardation, while in adults it causes hypogonadism and "white Addison's disease" (adrenal insufficiency without skin hyperpigmentation).
Hyperpituitarism and Types of Adenomas
Hormone excess is most commonly caused by adenomas. By diameter, they are divided into microadenomas (under 10 mm) and macroadenomas (10 mm and larger). A definitive diagnosis is made only based on electron microscopy and immunohistochemistry.
Prolactin-secreting adenoma. The most common (microadenoma composed of chromophobic cells). Leads to infertility, decreased libido, and in women, galactorrhea and amenorrhea.
Somatotropic adenoma. Caused by a mutation in the GNAS gene. In children, it provokes gigantism; in adults, acromegaly. Patients develop enlarged hands, feet, jaws, and tongue (macroglossia). Arterial hypertension, steroid diabetes, immunodeficiency, and premature atherosclerosis develop (due to increased LDL, VLDL, and ketone bodies).
Corticotropic adenoma. A basophilic tumor producing ACTH. Triggers Cushing's disease (upper-body obesity with thin extremities, striae, osteoporosis, hypertension).
Gonadotropic and thyrotropic adenomas. Rare; they cause hypogonadism and hyperthyroidism (with a risk of neck tissue compression), respectively.
Neurohypophyseal Pathology
Posterior lobe diseases are rarely diagnosed and are associated with impaired antidiuretic hormone (ADH) secretion.
Diabetes insipidus. Develops due to ADH deficiency against the background of tumors, infections, or trauma. Key symptoms include extreme thirst and the excretion of massive volumes of hypoosmolar urine (over 3 liters per day). Secondary diabetes insipidus can occur in liver and kidney diseases (the sites of ADH inactivation).
Syndrome of inappropriate antidiuretic hormone secretion (SIADH, or Parhon syndrome). The opposite condition, caused by ADH excess. Characterized by generalized edema, oliguria, decreased blood sodium levels, and water intoxication (headaches, nausea).
Malignant Pituitary Tumors
Pituitary carcinomas account for only about 1% of all neoplasms of the gland.
As a rule, they are hormonally inactive.
Microscopically, they consist of small chromophobic cells with pleomorphic nuclei and numerous mitoses.
Malignancy can often be reliably confirmed only after metastases are identified.
Carcinomas metastasize predominantly within the cranium (spread to bones, liver, or lymph nodes is extremely rare).
Mnemonic
The components of Wolfram syndrome are easily remembered via the acronym DIDMOAD: Diabetes insipidus, Diabetes mellitus, Optic atrophy, and Deafness.
Frequently asked questions
How does Cushing's disease differ from Cushing's syndrome?
The main difference lies in the localization of the primary pathological process and the blood level of adrenocorticotropic hormone (ACTH).
Feature
Cushing's Disease
Cushing's Syndrome
Localization
Pituitary tumor; a corticotropic adenoma produces ACTH and stimulates the adrenal glands
Primary process is located in the adrenal gland: corticosteroma or adrenocortical hyperplasia; ectopic ACTH secretion and iatrogenic syndrome from prolonged corticosteroid administration are also described
ACTH level
High
Usually decreased in primary adrenal pathology via negative feedback
Glucocorticoid level
High
High
What types of secretory cells are distinguished in the adenohypophysis, and what hormones do they produce?
Adenohypophyseal cells are classified by the tinctorial properties of their cytoplasm:
Chromophobic cells — poorly stained; generally do not secrete hormones, though some authors suggest their involvement in ACTH synthesis.
Basophilic cells — stain with basic dyes; corticotropic adenomas consist of large basophilic cells and are associated with ACTH production.
Acidophilic / eosinophilic cells — stain with acidic dyes; somatotropic adenomas consist of large eosinophilic cells and are associated with GH production.
Cells with lobulated nuclei — a minor population of 2–5%; their tinctorial properties may vary, with a lobulated nuclear structure being the constant feature.
Also, hormonally active adenomas of the adenohypophysis include: prolactinoma (produces prolactin), gonadotropic adenoma (associated with elevated FSH and less frequently LH), and thyrotropic adenoma (causes hyperthyroidism).
Which immunohistochemical markers are used to verify pituitary adenoma types?
Immunohistochemical verification of pituitary adenoma types uses markers against specific hormones contained in the cytoplasmic secretory granules.
Depending on the tumor type, expression of the following hormones is detected:
Prolactin (in prolactin-secreting adenomas);
ACTH (adrenocorticotropic hormone);
GH (growth hormone);
LH (luteinizing hormone);
FSH (follicle-stimulating hormone);
TSH (thyroid-stimulating hormone).
What is the difference between pituitary microadenomas and macroadenomas?
The classification is based on tumor size: microadenomas have a diameter of up to 10 mm, while macroadenomas are 10 mm and larger. Furthermore, macroadenomas may fill the entire sella turcica.
Why does autoimmune damage develop in Sheehan syndrome?
Tissue necrosis leads to the appearance of abnormal proteins in the blood. Because the pituitary lacks a blood-brain barrier, the immune system reacts to them and triggers autoimmune inflammation.
What physical appearance is characteristic of a patient with a corticotropic adenoma?
Cushing's disease develops: progressive truncal and facial obesity with disproportionately thin extremities (due to muscle atrophy), along with purple skin striae.
Go deeper
Mechanism of secondary immunodeficiency development in somatotropic adenoma
Differential diagnosis of adenoma types using electron microscopy
Histological differences among chromophobic, basophilic, and eosinophilic pituitary cells
Impact of hypopituitarism on lipid and carbohydrate metabolism
Pathogenesis of impaired glucose tolerance in SIADH (hyponatremic syndrome)