Pituitary Disorders — Causes, Symptoms, Diagnosis & Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

The pituitary gland — a pea-sized structure located at the base of the brain in the sella turcica — is the master endocrine gland, regulating growth hormone (GH), prolactin, ACTH (cortisol axis), TSH (thyroid axis), FSH and LH (gonadal axis), and ADH (antidiuretic hormone/vasopressin — produced in the hypothalamus but stored in the posterior pituitary). Pituitary disorders include pituitary adenomas (benign tumours — the most common), hypopituitarism (deficiency of one or more pituitary hormones), Cushing's disease (ACTH-secreting adenoma causing cortisol excess), acromegaly (GH-secreting adenoma causing growth hormone excess in adults), prolactinoma (prolactin-secreting adenoma — the most common functioning pituitary tumour), diabetes insipidus (ADH deficiency or resistance), and empty sella syndrome. Pituitary disorders can cause symptoms through hormone excess, hormone deficiency, or mass effect on adjacent structures (optic chiasm — causing visual field defects).

Pituitary adenomas: benign monoclonal tumours classified by size (microadenoma less than 10 mm; macroadenoma 10 mm or above) and secretory status. Most are sporadic; rarely familial (MEN1 syndrome — parathyroid, pituitary, pancreatic tumours; FIPA — familial isolated pituitary adenoma from AIP mutations; Carney complex). Prolactinoma (50% of pituitary adenomas): causes hyperprolactinaemia — menstrual irregularity and galactorrhoea in women, hypogonadism and erectile dysfunction in men. GH-secreting adenoma (15-20%): causes acromegaly in adults (gigantism in children with open epiphyses). ACTH-secreting adenoma (10-15%): causes Cushing's disease (hypercortisolaemia). Non-functioning adenomas (25-30%): cause hypopituitarism and mass effects. Hypopituitarism: caused by pituitary adenomas (direct compression), craniopharyngioma, pituitary surgery or radiotherapy, traumatic brain injury (common and underdiagnosed), subarachnoid haemorrhage (Sheehan's syndrome post-partum haemorrhage), infiltrative diseases (sarcoidosis, histiocytosis), and autoimmune hypophysitis (increasing recognition, may be triggered by immune checkpoint inhibitor therapy).

Mass effect from large pituitary adenomas: bitemporal hemianopia (loss of temporal visual fields from optic chiasm compression — the most characteristic sign), diplopia (cranial nerve III, IV, VI palsy from cavernous sinus invasion), headache (from dural stretching), and hypopituitarism (from normal pituitary tissue compression). Prolactinoma: women — amenorrhoea/oligomenorrhoea, galactorrhoea (milk discharge outside pregnancy), infertility, osteoporosis; men — reduced libido, erectile dysfunction, hypogonadism (often presenting late due to subtle symptoms), rarely galactorrhoea. Acromegaly (GH excess): gradual coarsening of facial features, jaw prognathism, enlarged hands and feet (increasing ring/shoe size), macroglossia, hyperhidrosis, joint pain, sleep apnoea, carpal tunnel syndrome, hypertension, diabetes mellitus, and cardiomegaly — diagnosis often delayed 5-10 years due to insidious onset. Cushing's disease (cortisol excess): central obesity, moon face, buffalo hump, striae, skin thinning, proximal myopathy, hypertension, type 2 diabetes, osteoporosis, depression, and immunosuppression. Hypopituitarism: features depend on which hormones are deficient — adrenal insufficiency (fatigue, hypotension, hyponatraemia — can be life-threatening) and hypothyroidism are most serious; GH deficiency causes reduced quality of life, fatigue, dyslipidaemia; gonadal deficiency causes infertility and osteoporosis. Diabetes insipidus: polydipsia and polyuria (large volumes of dilute urine).

MRI pituitary (with gadolinium, dedicated pituitary protocol): the gold standard for imaging the pituitary gland — identifies adenoma size, position, cavernous sinus invasion (Knosp grade), and optic chiasm proximity. Dynamic CT is used when MRI is contraindicated. Inferior petrosal sinus sampling (IPSS): if Cushing's disease is confirmed but pituitary MRI is negative or equivocal — measures ACTH gradient from petrosal sinuses relative to peripheral blood after CRH stimulation to lateralise the adenoma. Hormone assessment: serum prolactin (diagnostic for prolactinoma; above 5,000 mU/L is virtually pathognomonic; avoid 'hook effect' with 1:100 dilution in very large adenomas); serum IGF-1 (screening for acromegaly — GH excess stimulates hepatic IGF-1 production; confirms acromegaly if elevated); oral glucose tolerance test with GH levels (GH suppression below 0.4 mcg/L normally; failure to suppress confirms acromegaly); late-night salivary cortisol, 24-hour urinary free cortisol, and 1 mg overnight dexamethasone suppression test (screen for Cushing's); pituitary hormone profile (9 am cortisol, TSH, free T4, FSH, LH, testosterone/oestradiol, GH, IGF-1, prolactin) for hypopituitarism assessment. Formal visual field testing (automated perimetry) for macroadenomas near the optic chiasm.

Prolactinoma: dopamine agonists (cabergoline — preferred over bromocriptine due to greater efficacy, once/twice weekly dosing, and better tolerability) are first-line treatment for both micro- and macroprolactinomas; normalise prolactin in 85-90%, shrink tumour in 70-80%; surgery reserved for resistance or intolerance. Acromegaly: transsphenoidal surgery (TSS) is first-line if the adenoma is potentially resectable — achieves biochemical cure (IGF-1 normalisation) in approximately 50% of macroadenomas; somatostatin analogues (octreotide LAR, lanreotide — monthly depot injections) as primary treatment if surgery is not possible or after unsuccessful surgery; GH receptor antagonist (pegvisomant) for persistent acromegaly; radiotherapy (stereotactic radiosurgery — Gamma Knife) for residual tumour. Cushing's disease: transsphenoidal surgery is first-line — remission in 65-80% of microadenomas; bilateral adrenalectomy for persistent/recurrent disease; steroidogenesis inhibitors (metyrapone, ketoconazole, pasireotide) bridge therapy. Non-functioning macroadenomas: surgery if causing visual compromise or hypopituitarism; observation with regular MRI for smaller adenomas. Hypopituitarism hormone replacement: hydrocortisone (adrenal insufficiency — life-saving, patient must carry emergency injection kit); levothyroxine (hypothyroidism); testosterone or sex steroid replacement; GH replacement (adults — improves quality of life, body composition, and cardiovascular risk profile); desmopressin (DDAVP — synthetic ADH) for diabetes insipidus.

Hypopituitarism (panhypopituitarism) — deficiency of multiple anterior pituitary hormones — develops from pituitary macroadenoma mass effect, post-surgical damage, radiotherapy, or apoplexy; it is life-threatening when the ACTH-cortisol axis is deficient (adrenal crisis) and requires lifelong glucocorticoid replacement and peri-operative stress doses. GH, TSH, LH/FSH, and prolactin deficiency have important additional long-term consequences (reduced muscle mass, hypothyroidism, hypogonadism, infertility). Pituitary apoplexy — acute haemorrhage or infarction into a pituitary adenoma — presents as sudden severe headache ('thunderclap'), vomiting, visual loss, ophthalmoplegia, and altered consciousness; it is a neurosurgical emergency requiring immediate high-dose IV hydrocortisone, visual field assessment, and urgent MRI to determine whether emergency transsphenoidal decompression is required. Visual field defects from chiasmal compression by expanding pituitary macroadenoma — classically bitemporal hemianopia (superior then full bitemporal hemianopia as the tumour grows from below the chiasm) — require prompt surgical decompression to prevent permanent visual loss; severe optic atrophy from prolonged compression is irreversible. Acromegaly complications: untreated GH excess causes severe cardiovascular disease (hypertrophic cardiomyopathy, hypertension — in 50%), sleep apnoea (65%), arthropathy (60% — particularly weight-bearing joints), colorectal cancer (3-fold increased risk), and 2 to 3-fold increased overall mortality versus the general population. Cushing's disease complications: see adrenal disorders. Craniopharyngioma (suprasellar tumour causing pituitary dysfunction) frequently causes permanent panhypopituitarism and visual impairment from its location and the damage caused by surgical excision.

Most pituitary disorders cannot be prevented. Key management principles: MEN1 genetic screening for first-degree relatives of affected individuals (enables early detection of pituitary, parathyroid, and pancreatic tumours). Annual pituitary hormone profile and MRI surveillance for patients with known adenomas on conservative management. After pituitary surgery, monitor for hypopituitarism — adrenal insufficiency is an early post-operative concern (hydrocortisone stress doses required during illness, surgery, or procedures). Bone density DEXA scanning for all patients with hypopituitarism or Cushing's (high fracture risk). Screen for cardiovascular risk factors in acromegaly (hypertension, diabetes, sleep apnoea). Cancer screening: acromegaly patients have increased colorectal cancer risk — colonoscopy recommended at diagnosis and 5-yearly.

Seek urgent ophthalmological and neurosurgical assessment for sudden visual field loss (bitemporal hemianopia) or acute severe headache with visual changes, which may indicate pituitary apoplexy (sudden haemorrhage or infarction of a pituitary adenoma — a neuroendocrine emergency). Consult an endocrinologist for: unexplained menstrual irregularity with galactorrhoea (prolactinoma); progressive change in facial appearance, jaw, or hand/foot size (acromegaly); central obesity with striae and easy bruising (Cushing's syndrome); severe fatigue, low blood pressure, or hyponatraemia (pituitary adrenal insufficiency); and any incidentally found pituitary lesion on brain imaging. Adrenal insufficiency from hypopituitarism is potentially life-threatening during intercurrent illness — patients need emergency hydrocortisone and should wear a medical alert bracelet.