Cushing’s disease is a clinical syndrome triggered by hypersecretion of adrenocorticotropic hormone (ACTH) from pituitary ACTH-secreting adenomas, which subsequently causes adrenal cortical hyperplasia and excess cortisol production. It accounts for 70%–80% of all etiologies of Cushing’s Syndrome (Chinese Guidelines for the Diagnosis and Treatment of Pituitary Adenomas, 2024).

I. Core Pathological Mechanism of Cushing’s Disease: Excessive ACTH Secretion

Cushing’s disease refers to a clinical syndrome arising from aberrant ACTH overproduction by pituitary ACTH adenomas, inducing adrenal cortical hyperplasia and cortisol excess, responsible for 70%–80% of Cushing’s Syndrome cases (Chinese Guidelines for the Diagnosis and Treatment of Pituitary Adenomas, 2024).

Normal pituitary ACTH secretion is regulated by hypothalamic corticotropin-releasing hormone (CRH). However, adenoma cells lose negative feedback inhibition, resulting in persistently elevated serum ACTH levels (normal range: 10–60 pg/mL; patients may reach 200–500 pg/mL). This further stimulates hyperplasia of the zona fasciculata of the adrenal cortex, boosting cortisol secretion to 2–5 times the physiological baseline.

Excess cortisol exerts pathological effects across multiple bodily systems:

Glucose metabolism: Promotes hepatic gluconeogenesis and inhibits peripheral glucose uptake. Approximately 60% of patients develop elevated fasting blood glucose (≥7.0 mmol/L), and 25% progress to pituitary diabetes mellitus.

Protein metabolism: Accelerates skeletal muscle protein breakdown, causing limb muscular atrophy in 45% of patients. It also drives fat redistribution, leading to central obesity.

Electrolyte homeostasis: Cortisol exhibits weak mineralocorticoid activity. Thirty percent of patients develop hypokalemia (<3.5 mmol/L), presenting with fatigue and muscle weakness.

II. Prolactinomas: Classic Manifestations of Sex Hormone Dysregulation

(I) Pathogenesis of Amenorrhea-Galactorrhea Syndrome in Females

Prolactinomas are the most prevalent functional pituitary adenomas, constituting 30%–40% of all pituitary neoplasms. Their incidence in women is 5–10 times higher than that in men (data from Ruijin Hospital, Shanghai, 2024). Tumor cells overproduce prolactin (PRL): normal PRL levels in healthy women are <25 ng/mL, while affected patients may show concentrations ranging from 200 to 1000 ng/mL. Hyperprolactinemia disrupts the reproductive axis via two pathways:

Suppression of the hypothalamic-pituitary-gonadal axis: Inhibits pulsatile gonadotropin-releasing hormone (GnRH) secretion, lowering follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels and impairing ovarian ovulation. Among women of childbearing age, 85% develop oligomenorrhea or amenorrhea (menstrual cycles longer than 35 days, or absence of menses for ≥3 months).

Mammary gland stimulation: Directly binds to prolactin receptors on mammary epithelial cells, causing non-lactational galactorrhea (unilateral or bilateral milky discharge, prominent upon nipple compression) in 60% of patients.

(II) Subclinical Hypogonadism in Male Patients

Male prolactinoma patients account for 15%–20% of all prolactinoma cases and often experience delayed diagnosis due to insidious symptoms, primarily including:

Hypogonadism: Reduced testosterone levels (<3.5 nmol/L; normal reference: 4.5–8.2 nmol/L), leading to decreased libido (70%) and erectile dysfunction (55%). Gynecomastia (male breast enlargement) occurs in 30% of cases.

Impaired sperm quality: Deficient FSH and LH disrupt spermatogenesis. Semen analysis reveals sperm concentration <15×10⁶/mL (normal ≥15×10⁶/mL) and progressive motility <40% (normal ≥40%).

III. Growth Hormone Adenomas: Acromegaly and Excessive Somatic Growth

(I) Characteristic Alterations in Adult Acromegaly

Growth hormone (GH) adenomas make up 10%–15% of pituitary adenomas. Overproduction of GH (normal <5 ng/mL; patients: 20–100 ng/mL) and elevated insulin-like growth factor-1 (IGF-1, >358 ng/mL) trigger hyperplasia of soft tissues, bones and visceral organs throughout the body. Typical manifestations include:

Facial and bodily deformities: Thickened supraorbital ridges (80%), prognathism (65%), deepened nasolabial folds, enlarged sausage-like fingers and toes (70%), rough skin and hyperhidrosis (55%).

Visceromegaly: Macroglossia causing slurred speech (40%), cardiomegaly with chest tightness and palpitations (30%), and hepatosplenomegaly (ultrasound shows liver/kidney volume increased by 20%–30% relative to normal).

Metabolic derangements: GH antagonizes insulin action; 45% of patients develop impaired glucose tolerance, 20% progress to diabetes mellitus, and dyslipidemia (triglycerides >1.7 mmol/L) affects 60% of patients.

(II) Accelerated Linear Growth in Childhood-Onset Cases

When GH adenomas develop before epiphyseal closure (patients under 18 years old), excess GH drives rapid longitudinal growth, with annual height gain exceeding 10 cm (normal range: 4–6 cm). Final adult height surpasses the 97th percentile for peers (Chinese Journal of Pediatrics, 2025). Associated soft tissue hyperplasia includes macroglossia (50%) and enlarged hands/feet, alongside bone age advancement by 2–3 years (X-ray imaging indicates a 3-fold higher risk of premature epiphyseal closure).

IV. Classic Signs of Cushing’s Syndrome: Mechanism Underlying Central Obesity

(I) Pathogenesis of Abnormal Fat Distribution

Cortisol promotes lipogenesis and redistributes adipose tissue, producing two hallmark phenotypes:

Truncal adiposity: Predominant abdominal fat accumulation, with waist-to-hip ratio >0.9 in females and >1.0 in males, resulting in buffalo hump (75%) and moon facies (80%).

Peripheral lipoatrophy: Increased breakdown of fat and muscle in extremities, forming the characteristic body habitus of central adiposity with thin limbs. Wide violaceous striae (>1 cm in width) appear on the medial thighs in 60% of patients, caused by cortisol-induced rupture of dermal collagen fibers.

(II) Cardiovascular Complications from Chronic Hypercortisolemia

Prolonged elevated cortisol levels induce:

Hypertension (80% incidence): Mediated by sodium and water retention plus enhanced vascular sensitivity to catecholamines; systolic blood pressure typically ranges 150–180 mmHg, diastolic pressure 90–110 mmHg.

Atherosclerosis: Elevated low-density lipoprotein cholesterol (LDL-C >3.4 mmol/L) and reduced high-density lipoprotein cholesterol (HDL-C <1.0 mmol/L). The risk of coronary heart disease is 2–3 times higher than the general population (Chinese Journal of Endocrinology and Metabolism, 2024).

V. Differential Diagnosis Between Cushing’s Disease and Other Pituitary Adenoma Subtypes

(I) Prolactinoma vs. Cushing’s Disease

(II) Growth Hormone Adenoma vs. Cushing’s Disease

FAQ: Abnormal Hormone Secretion in Pituitary Adenomas

1. Could obesity be a sign of Cushing’s Disease?

Yes. The hallmark feature of Cushing’s Disease is central obesity (fat accumulation in the abdomen and back with relatively slender extremities), frequently accompanied by hypertension, skin striae and menstrual irregularities. Patients presenting with truncal weight gain combined with violaceous striae, acne or persistent fatigue should undergo screening tests including 24-hour urinary free cortisol assay and pituitary MRI to rule out Cushing’s Disease.

2. What adverse outcomes arise from aberrant hormone secretion by pituitary adenomas?

Complications vary by adenoma subtype:

Prolactinomas: Amenorrhea and galactorrhea in women, hypogonadism in men; long-standing hyperprolactinemia increases osteoporosis risk.

Growth hormone adenomas: Acromegaly with facial disfigurement and visceromegaly in adults; pathological rapid growth in pediatric patients.

Cushing’s Disease: Central obesity, hypertension, diabetes mellitus and osteoporosis, with drastically elevated cardiovascular disease risk.

Early diagnosis and hormone normalization significantly improve long-term prognosis; delayed treatment may lead to irreversible organic damage to multiple organs.