A 38-year-old man from Bangalore presents with recurrent nephrolithiasis and persistent hypertension (BP 158/96 mmHg). Serum calcium is 11.2 mg/dL (normal 8.5–10.5), phosphate 2.8 mg/dL, and PTH 185 pg/mL (normal 15–65). On further questioning, he reports a 3-year history of recurrent peptic ulcer disease refractory to standard PPI therapy, and his 12-year-old son has recently been diagnosed with a pituitary adenoma secreting growth hormone. Imaging of the parathyroid glands shows a 1.8 cm nodule. What is the most likely diagnosis?

Explanation

## Diagnosis: MEN 1 Syndrome ### Clinical Features Present **Key Point:** MEN 1 is characterized by the **3 P's**: Parathyroid adenoma, Pancreatic neuroendocrine tumors (PNETs), and Pituitary adenoma. This patient demonstrates all three cardinal features: | Feature | Clinical Finding | Mechanism | |---------|------------------|----------| | **Parathyroid** | Primary hyperparathyroidism (elevated PTH, hypercalcemia, nephrolithiasis) | Parathyroid adenoma (multiglandular involvement common) | | **Pancreatic** | Recurrent peptic ulcer disease | Gastrinoma (Zollinger-Ellison syndrome) — most common functional PNET in MEN 1 | | **Pituitary** | Son with GH-secreting pituitary adenoma | Familial inheritance; prolactinoma and GH-secreting adenomas are common | ### Pathophysiology **High-Yield:** MEN 1 is caused by **loss-of-function mutations in the MEN1 gene** (chromosome 11q13), which encodes **menin**, a tumor suppressor protein. This leads to: 1. Inactivation of p27 (CDK inhibitor) → uncontrolled cell proliferation 2. Impaired histone deacetylase function → altered gene expression 3. **Multiglandular involvement** (not single adenoma) — distinguishes from sporadic disease ### Diagnostic Criteria **Mnemonic: "3 P's of MEN 1"** - **P**arathyroid adenoma (95% of patients by age 50) - **P**ancreatic/GI neuroendocrine tumors (60–70%) - **P**ituitary adenoma (30–40%) Other associated tumors: adrenal adenomas (40%), carcinoid tumors (thymic, bronchial, gastric), cutaneous manifestations (lipomas, collagenomas, angiofibromas). ### Clinical Pearl **Familial clustering is key:** The patient's son with pituitary adenoma strongly suggests inherited MEN 1 rather than sporadic disease. Genetic counseling and screening of first-degree relatives (serum calcium, PTH, prolactin, gastrin fasting level) is mandatory. ### Management - **Parathyroid:** Subtotal parathyroidectomy or total parathyroidectomy with autotransplantation - **Gastrinoma:** Proton pump inhibitors (control acid hypersecretion); consider surgical resection if localized - **Pituitary:** Dopamine agonists (prolactinoma); surgery/radiotherapy for GH-secreting adenomas - **Surveillance:** Annual biochemical screening; imaging every 2–3 years [cite:Robbins 10e Ch 24]