A 42-year-old man who is employed as a construction worker presents to his primary care physician with complaints of moderate headaches and profuse sweating. He reports the need to carry up to 3 additional shirt changes to work because they drench quickly even with tasks of low physical exertion. His coworkers have commented about his changing glove and boot sizes, which have increased at least 4 times since he joined the company 10 years ago. Physical examination is unremarkable except for blood pressure of 160/95 mm Hg, hyperhidrosis, noticeably large pores, hypertrichosis, widely spaced teeth, and prognathism. Which of the following best explains the patient’s clinical manifestations?

Increased serum insulin-like growth factor 1 (IGF-1)

Increased thyroid-stimulating hormone

A 61-year-old male presents to an urgent care clinic with the complaints of pain in his joints and recurrent headaches for a month. He is also currently concerned about sweating excessively even at room temperature. His wife, who is accompanying him, adds that his facial appearance has changed over the past few years as he now has a protruding jaw and a prominent forehead and brow ridge. His wedding ring no longer fits his finger despite a lack of weight gain over the last decade. His temperature is 98.6° F (37° C), respirations are 15/min, pulse is 67/min and blood pressure is 122/88 mm Hg. A general physical exam does not show any abnormality. What lab findings are most likely to be seen in this patient?

Elevated insulin-like growth factor (IGF1) and growth hormone (GH)

Four months after giving birth, a young woman presents to the hospital complaining of lack of breast milk secretion. The patient complains of constantly feeling tired. Physical exam reveals that she is slightly hypotensive and has lost a significant amount of weight since giving birth. The patient states that she has not experienced menstruation since the birth. Which of the following is likely to have contributed to this patient's presentation?

Increased anterior pituitary perfusion

Pregnancy-induced decrease in anterior pituitary size

A 34-year-old woman, who had her first child 2 weeks ago, visits her family physician with concerns about constant fatigue and difficulty with breastfeeding. She was discharged from the intensive care unit after hospitalization for severe postpartum hemorrhage. Since then, she has tried multiple pumps and self-stimulation to encourage breast milk production; however, neither of these strategies has worked. Her blood pressure is 88/56 mm Hg and heart rate is 120/min. Which of the following best explains the underlying condition of this patient?

Pituitary infiltration by histiocytes

Pituitary stalk epithelial tumor

A 48-year-old man is brought to the emergency department by his neighbor, who found him lying unconscious at the door of his house. The patient lives alone and no further history is available. On physical examination, his temperature is 37.2ºC (98.9ºF), pulse rate is 114/min, blood pressure is 116/78 mm Hg, and respiratory rate is 22/min. His Glasgow Coma Scale score is 7 and the patient is intubated. A stat serum osmolality is reported at 260 mmol/kg. Based on the provided information, which of the following conditions is most likely present in this patient?

Syndrome of inappropriate antidiuretic hormone

Nonketotic hyperosmolar hyperglycemic coma

Pituitary disorders for USMLE Step 2 CK: High-Yield Internal Medicine Lessons

Pituitary Essentials - The Master Controller

Pituitary gland, optic chiasm, and tumor

Anterior Lobe (Adenohypophysis)
- Hormones: 📌 FLAT PiG: FSH, LH, ACTH, TSH, Prolactin, ignore, GH.
- Regulated by hypothalamic releasing/inhibiting hormones.
Posterior Lobe (Neurohypophysis)
- Stores & secretes: Vasopressin (ADH) & Oxytocin.
Pituitary Adenomas
- Most common cause of pituitary hormone excess/deficiency.
- Microadenoma (< 1 cm) vs. Macroadenoma (≥ 1 cm).
- Mass effect (macroadenomas): Bitemporal hemianopsia, headache.

⭐ Prolactinomas are the most common pituitary adenoma. Excess prolactin suppresses GnRH, leading to ↓FSH & ↓LH, causing amenorrhea, galactorrhea, and infertility.

Anterior Hyperpituitarism - Gland Overdrive

Etiology: Primarily caused by pituitary adenomas. Classified by size: microadenomas (<10 mm) or macroadenomas (≥10 mm).
Syndromes by Hormone Excess:
- Prolactinoma (Most Common): ↑Prolactin.
  - Females: Galactorrhea, amenorrhea, infertility.
  - Males: ↓Libido, erectile dysfunction, gynecomastia.
  - Treatment: Dopamine agonists (e.g., Cabergoline).
- Somatotroph Adenoma: ↑Growth Hormone (GH).
  - Children: Gigantism (pre-epiphyseal closure).
  - Adults: Acromegaly (coarse facial features, large hands/feet, glucose intolerance).
- Corticotroph Adenoma: ↑ACTH, causing Cushing's Disease.

Acromegaly: Signs and Symptoms

⭐ Diagnosis of Acromegaly: The best initial test is measuring IGF-1 levels. The most specific diagnostic test is the failure to suppress serum GH following an oral glucose tolerance test (OGTT).

Anterior Hypopituitarism - Running on Empty

Etiology: Most commonly due to non-functioning pituitary adenomas. Other causes include Sheehan syndrome (postpartum necrosis), apoplexy (hemorrhage/infarction), iatrogenic (surgery, radiation), and infiltrative diseases (e.g., sarcoidosis, hemochromatosis).
Clinical Presentation: Varies with deficient hormones. Order of loss is often predictable.
- GH: Fatigue, weakness, ↑fat mass (often first sign in adults).
- LH/FSH: ↓ Libido, amenorrhea/erectile dysfunction, infertility.
- TSH: Secondary hypothyroidism (fatigue, cold intolerance).
- ACTH: Secondary adrenal insufficiency (weakness, hypotension).
- 📌 Mnemonic for order of loss: "Go Look For The Adenoma" (GH, LH/FSH, TSH, ACTH).
Diagnosis: Low basal hormone levels (e.g., 8 AM cortisol, TSH, free T4) plus stimulation tests (e.g., ACTH stimulation test). Pituitary MRI to identify the cause.

⭐ In secondary adrenal insufficiency from hypopituitarism, hyperpigmentation is absent because ACTH and MSH levels are low. Aldosterone secretion is preserved (RAAS control).

Sagittal MRI: Empty Sella Turcica

Posterior Pituitary - Water Woes

Antidiuretic Hormone (ADH/Vasopressin): Regulates plasma osmolality by controlling renal water reabsorption. Imbalance leads to Diabetes Insipidus (DI) or SIADH.

Feature	Central DI	Nephrogenic DI	SIADH
ADH Level	↓ Low	Normal / ↑ High	↑ High (inappropriate)
Serum Osm	>295 mOsm/kg	>295 mOsm/kg	<275 mOsm/kg
Urine Osm	< Serum Osm	< Serum Osm	> Serum Osm
Urine Na+	Variable	Variable	>40 mEq/L
Treatment	Desmopressin	Thiazides, NSAIDs	Fluid restriction, Vaptans

⭐ Ectopic ADH production, most commonly from Small Cell Lung Cancer, is a classic cause of SIADH. Always consider malignancy in a patient with unexplained hyponatremia and concentrated urine.

High‑Yield Points - ⚡ Biggest Takeaways

Prolactinoma, the most common pituitary tumor, causes galactorrhea; treat with dopamine agonists.

For acromegaly, the best initial test is IGF-1; a glucose suppression test confirms the diagnosis.

Cushing's disease is an ACTH-secreting adenoma suppressible by high-dose dexamethasone.

Sheehan syndrome is postpartum pituitary necrosis causing failure to lactate.

Central DI responds to desmopressin; nephrogenic DI does not.

SIADH causes euvolemic hyponatremia; treat with fluid restriction.

Pituitary adenomas cause bitemporal hemianopsia via optic chiasm compression.

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