Endocrine · Year 2 · from Endocrine

Case 1: Pituitary Macroadenoma with Visual Field Defects

Patient Demographics

  • Age: 52 years
  • Sex: Female
  • Occupation: Accountant

Chief Complaint

"I've been having headaches and bumping into things on my sides."

History of Present Illness

A 52-year-old woman presents with a 6-month history of worsening headaches and progressive visual difficulties. She reports bumping into door frames and has had two minor car accidents when changing lanes because she did not see vehicles approaching from the side. Her husband has noticed that she has been more fatigued and has lost interest in activities she previously enjoyed. She also reports amenorrhea for the past 8 months, which she attributed to menopause.

Physical Examination

  • Vital Signs: BP 118/72 mmHg, HR 58 bpm, Temp 36.4°C
  • General: Appears fatigued, pale complexion
  • HEENT: Visual field testing reveals bitemporal hemianopia
  • Neurologic: Cranial nerves otherwise intact, no papilledema
  • Skin: Dry, cool to touch

Workup

  • Laboratory Studies:
  • TSH: 0.8 mIU/L (low-normal)
  • Free T4: 0.6 ng/dL (low, normal 0.9-1.7)
  • Prolactin: 85 ng/mL (elevated, normal <25)
  • Cortisol (8 AM): 4.2 μg/dL (low, normal 6-23)
  • FSH: 2.1 mIU/mL (low for postmenopausal)
  • LH: 1.8 mIU/mL (low for postmenopausal)
  • IGF-1: 65 ng/mL (low for age)
  • MRI Brain with Contrast: 2.5 cm pituitary macroadenoma with suprasellar extension compressing the optic chiasm

Diagnosis

Non-functioning pituitary macroadenoma causing:

  1. Bitemporal hemianopia (optic chiasm compression)
  2. Hypopituitarism (secondary hypothyroidism, secondary adrenal insufficiency, secondary hypogonadism, GH deficiency)
  3. Stalk effect hyperprolactinemia (disruption of dopamine inhibition)

Treatment

  1. Immediate stress-dose glucocorticoids (hydrocortisone 100 mg IV) given before any other intervention
  2. Transsphenoidal surgical resection of the adenoma
  3. Post-operative hormone replacement:
  • Hydrocortisone replacement started BEFORE levothyroxine
  • Levothyroxine for secondary hypothyroidism
  • Estrogen/progesterone therapy consideration
  1. Close monitoring for post-operative diabetes insipidus

Clinical Pearl

The mild prolactin elevation (85 ng/mL) in this case represents "stalk effect" rather than a true prolactinoma. The tumor is compressing the pituitary stalk, interrupting dopamine delivery to lactotrophs. A true prolactinoma of this size would typically produce prolactin levels >200 ng/mL. This distinction is critical because prolactinomas respond to dopamine agonist therapy, while non-functioning adenomas require surgery for mass effect.

Clinical Image

Coronal T1-weighted MRI with gadolinium showing a pituitary macroadenoma with suprasellar extension and optic chiasm compression.

Image Source: Wikimedia Commons - "Pituitary macroadenoma" by Hellerhoff License: CC BY-SA 3.0 URL: https://commons.wikimedia.org/wiki/File:Hypophysenadenom_MRT_coronar.jpg

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