Pituitary Tumours

⚠️ In patients with low 9 am cortisol or inadequate short Synacthen response, always start steroid replacement first to cover stress – this is life-saving. 💡 Never start levothyroxine before hydrocortisone, as this can precipitate an Addisonian crisis.

📍 About

• Pituitary adenomas are benign monoclonal tumours of the anterior pituitary.
• Incidence: ~77 per 100,000, often detected incidentally on MRI (“incidentalomas”).
• Classified by size: microadenomas (<10 mm) vs macroadenomas (>10 mm).
• Can be functioning (hormone-secreting) or non-functioning (presenting via mass effect).

🧬 Aetiology & Risk

• Monoclonal benign tumours with genetic associations (e.g., MEN1, AIP mutations).
• Most are sporadic, but familial syndromes include MEN1, Carney complex, McCune-Albright.

📊 Common Types

• 🥛 Prolactinomas (~57%) – most common.
• 🔇 Non-functioning adenomas (~28%).
• 📏 GH-secreting (~11%) → acromegaly/gigantism.
• 🧃 ACTH-secreting (~2%) → Cushing’s disease.
• 🌀 TSH-secreting (<1%) → central hyperthyroidism (rare).

⚙️ Pathophysiology

• 📈 Hormone excess: e.g., hyperprolactinaemia → galactorrhoea/amenorrhoea; GH → IGF-1 excess; ACTH → cortisol overproduction.
• 📉 Hormone deficiency: mass effect compresses normal pituitary tissue ➝ secondary adrenal insufficiency, hypothyroidism, hypogonadism.
• 🧠 Mass effect: bitemporal hemianopia (optic chiasm compression), headache, ophthalmoplegia (cavernous sinus invasion).
• ❌ Very rare: diabetes insipidus (more typical of craniopharyngioma or after surgery).

🧾 Clinical Manifestations

• Hormonal excess: - Prolactinoma → galactorrhoea, amenorrhoea, infertility, erectile dysfunction. - GH-secreting → acromegaly (coarse features, prognathism, spade hands, organomegaly). - ACTH-secreting → Cushing’s disease (central obesity, striae, proximal weakness). - TSH-secreting → goitre, weight loss, tremor.
• Mass effect: Headache, bitemporal hemianopia, cranial nerve palsies.
• Hormonal deficiency: Fatigue, ↓ libido, infertility, cold intolerance, adrenal crisis.

🔎 Investigations

• 🧪 Baseline hormones: 9 am cortisol, prolactin, LH/FSH, testosterone/oestradiol, TFTs, IGF-1 (if acromegaly suspected).
• 🧪 Dynamic tests: - Short Synacthen test (adrenal function). - Low-dose dexamethasone suppression (Cushing’s). - OGTT with GH sampling (acromegaly diagnosis).
• 🖼️ Imaging: MRI pituitary with contrast (gold standard).
• 👁️ Visual fields: Goldman perimetry for optic chiasm compression.

💊 Management

• Prolactinomas: Dopamine agonists (cabergoline 1st line). Surgery if resistant or intolerant.
• Cushing’s disease (ACTH adenoma): Trans-sphenoidal surgery (first-line). If not curative ➝ medical therapy (ketoconazole, metyrapone) ± radiotherapy.
• Acromegaly: Trans-sphenoidal surgery ± somatostatin analogues (octreotide, lanreotide), pegvisomant (GH receptor antagonist), radiotherapy if persistent.
• Non-functioning adenomas: Surgery if compressive (vision loss, hydrocephalus). Otherwise monitor with MRI + visual fields.
• TSH adenomas: Surgery usually required; somatostatin analogues may help.

🩺 Hypopituitarism Replacement

• Adrenal axis: Hydrocortisone 10 mg AM, 5 mg midday, 5 mg PM. Stress dose during illness.
• Thyroid axis: Levothyroxine (monitor free T4, not TSH).
• Gonadal axis: Testosterone in men; oestrogen ± progesterone in women.
• Growth hormone deficiency: Recombinant GH (specialist only).
• ADH deficiency (DI): Desmopressin oral/nasal.

⚠️ Complications & Follow-Up

• Recurrence or regrowth ➝ long-term MRI surveillance.
• Hypopituitarism requiring lifelong replacement.
• Visual impairment from tumour regrowth.
• CSF leaks post-surgery.

📌 Exam Pearls

• Replace steroids before thyroxine in suspected hypopituitarism.
• Prolactinoma = most common functional adenoma.
• Macroadenomas → think mass effect; microadenomas → think hormonal effect.
• Hyperprolactinaemia may be drug-induced (antipsychotics, metoclopramide) – exclude before diagnosing prolactinoma.
• DI is rare in pituitary adenomas, more typical of craniopharyngioma, metastasis, or pituitary surgery.

Cases — Pituitary Tumours

• Case 1 — Prolactinoma 🍼: A 29-year-old woman presents with secondary amenorrhoea, galactorrhoea, and infertility. Exam: normal visual fields. Bloods: prolactin 4000 mU/L. MRI: 8 mm pituitary microadenoma. Diagnosis: prolactinoma. Managed with dopamine agonist (cabergoline); surgery rarely required.
• Case 2 — Non-functioning macroadenoma 🧠: A 62-year-old man presents with headaches and bitemporal hemianopia. Bloods: low cortisol, low T4, low testosterone, normal prolactin. MRI: large sellar mass compressing optic chiasm. Diagnosis: non-functioning pituitary macroadenoma with hypopituitarism. Managed with hormone replacement and trans-sphenoidal surgery.
• Case 3 — Acromegaly (GH-secreting tumour) ✋: A 45-year-old woman complains of increased shoe and ring size, coarse facial features, and joint pain. Exam: prognathism, enlarged hands. IGF-1 raised, oral glucose tolerance test fails to suppress GH. MRI: pituitary macroadenoma. Diagnosis: GH-secreting pituitary tumour (acromegaly). Managed with trans-sphenoidal resection, somatostatin analogues if persistent disease.
• Case 4 — ACTH-secreting tumour (Cushing’s disease) ⚡: A 38-year-old woman presents with weight gain, purple striae, proximal myopathy, and hypertension. Bloods: high cortisol not suppressed by low-dose dexamethasone, suppressed with high-dose dexamethasone. MRI: pituitary microadenoma. Diagnosis: ACTH-secreting pituitary tumour causing Cushing’s disease. Managed with trans-sphenoidal pituitary surgery.

Teaching Point 🩺: Pituitary tumours may be: - Functioning: prolactinomas (most common), GH-secreting (acromegaly), ACTH-secreting (Cushing’s disease). - Non-functioning: often present with mass effect (headache, visual field defects) and hypopituitarism. Investigations: hormonal profile, MRI pituitary, visual fields. Management: medical (dopamine agonists, somatostatin analogues), trans-sphenoidal surgery, radiotherapy.