Hypopituitarism (Pituitary Failure)

Related Subjects: |Adrenal Physiology |Addisons Disease |Phaeochromocytoma |Adrenal Adenomas |Adrenal Cancer |Cushing Syndrome |Cushing Disease |Congenital Adrenal hyperplasia |Primary hyperaldosteronism (Conn's syndrome) |ACTH |McCune Albright syndrome |Male Infertility |Prolactin |Prolactinoma |Sheehan's syndrome

⚠️ Always give stress-dose steroids (at least double maintenance) during illness, infection, trauma, or surgery. 💡 In suspected but undiagnosed hypopituitarism, administer steroids before pursuing investigations — cortisol replacement is lifesaving.

📖 About

• The anterior pituitary releases six key hormones 🧬: LH, FSH, GH, TSH, ACTH, Prolactin.

🧬 Causes of Hypopituitarism

• 🎭 Pituitary adenoma (non-functioning or hormone-secreting e.g. prolactinoma).
• 👶 Craniopharyngioma – common in children.
• 🌿 Infiltrative diseases: sarcoidosis, TB, haemochromatosis.
• 💉 Vascular: Sheehan’s syndrome (postpartum), pituitary apoplexy (acute infarction/bleed).
• 🦠 Infectious: meningitis, encephalitis, syphilis.
• 🤕 Trauma: esp. basal skull fractures.
• 🧬 Congenital: Kallmann syndrome (GnRH deficiency + anosmia).
• 🛡️ Autoimmune: anti-pituitary antibodies.
• ⚡ Other: anorexia, starvation, radiotherapy, chemotherapy.

🩺 Clinical Presentation

• ACTH deficiency 🧪: low cortisol → fatigue, hypotension. Mineralocorticoids preserved (distinguishes from Addison’s).
• Prolactin deficiency 🍼: impaired lactation; ↑ prolactin may signal stalk compression (“stalk effect”).
• LH & FSH deficiency ❤️: infertility, ↓ libido, amenorrhoea/impotence.
• GH deficiency 📏: children – short stature; adults – ↓ muscle bulk, energy.
• TSH deficiency 🌀: central hypothyroidism.
• ADH deficiency 💧: diabetes insipidus if posterior pituitary involved.

👁️ Local Effects of Pituitary Lesions

• Headache.
• Bitemporal hemianopia 👓 (optic chiasm compression).
• Cranial nerve palsies (III, IV, VI) if cavernous sinus involved.
• Pituitary hormone deficiencies.

🔍 Investigations

• Hormone profile: prolactin, TSH + T4, 9am cortisol, IGF-1, GH, FSH, LH, oestrogen/testosterone.
• Metabolic profile: fasting glucose, HbA1c.
• 🧲 MRI pituitary (gold standard for mass lesions).

💊 Management

• Acute hypopituitarism 🚨: IV hydrocortisone 100 mg q6h immediately.
• Hydrocortisone replacement 💉: oral 15–40 mg/day (e.g. 15 mg AM, 5 mg PM).
• Thyroid replacement 🌀: L-thyroxine titrated to normal T4 (not TSH, as central disease).
• Gonadal hormones ❤️:
  • Males: testosterone (IM/oral/gel/implant) if fertility not required; gonadotropins if fertility desired.
  • Females: oestrogen-progesterone if fertility not required; gonadotropins or pulsatile GnRH if fertility required.
• Growth hormone 📏: consider in children; in adults rarely used (possible malignancy risk).

📚 Exam Tip: - In acute hypopituitarism, give steroids first. - Central hypothyroidism → monitor with T4 (not TSH). - ACTH deficiency spares mineralocorticoids (unlike Addison’s).

Cases — Hypopituitarism (Pituitary Failure)

• Case 1 — Pituitary adenoma 🧠: A 48-year-old man presents with fatigue, erectile dysfunction, and reduced libido. Exam: bitemporal hemianopia. Bloods: low testosterone, low LH/FSH, low cortisol, low T4 with inappropriately normal TSH. MRI: large pituitary macroadenoma compressing the optic chiasm. Diagnosis: hypopituitarism secondary to pituitary adenoma. Managed with hormone replacement (hydrocortisone, thyroxine, testosterone) and trans-sphenoidal surgery.
• Case 2 — Sheehan’s syndrome 🩸: A 32-year-old woman presents 3 months after a postpartum haemorrhage with failure to lactate, secondary amenorrhoea, fatigue, and weight loss. Bloods: low prolactin, low gonadotropins, low cortisol, low T4. Diagnosis: postpartum pituitary necrosis (Sheehan’s syndrome). Managed with lifelong hormone replacement (hydrocortisone, thyroxine, oestrogen/progesterone replacement).
• Case 3 — Radiotherapy-induced ⚡: A 55-year-old man treated with cranial radiotherapy for nasopharyngeal carcinoma 10 years ago presents with progressive fatigue, cold intolerance, and reduced exercise tolerance. Bloods: low IGF-1, low cortisol, low T4, low gonadotropins. Diagnosis: panhypopituitarism secondary to radiotherapy. Managed with staged hormone replacement (hydrocortisone before thyroxine, then sex steroids, GH if appropriate).

Teaching Point 🩺: Hypopituitarism = partial or complete deficiency of pituitary hormones. Common causes: pituitary adenoma, surgery, radiotherapy, infarction (Sheehan’s), trauma, infiltrative disease. Clinical features depend on which hormones are deficient: - ACTH: fatigue, adrenal crisis. - TSH: hypothyroidism. - LH/FSH: infertility, amenorrhoea, low libido. - GH: reduced muscle mass, increased fat, low energy. - Prolactin: failure to lactate. Always replace hydrocortisone before thyroxine to avoid adrenal crisis.