A 42-year-old woman with bipolar I disorder on olanzapine 15 mg/day for 3 years presents with weight gain (12 kg), fasting glucose 118 mg/dL, and triglycerides 240 mg/dL. Which of the following metabolic/endocrine complications is NOT associated with olanzapine use?

Explanation

## Metabolic and Endocrine Side Effects of Olanzapine ### Established Metabolic Complications Olanzapine is among the **highest-risk atypical antipsychotics** for metabolic syndrome. The triad of weight gain, hyperglycemia, and dyslipidemia is well-documented. **Key Point:** Olanzapine's metabolic toxicity is thought to involve: 1. **Histamine H1 receptor antagonism** → increased appetite, weight gain 2. **5-HT2C receptor antagonism** → loss of satiety signaling 3. **Direct effects on pancreatic β-cells** → reduced insulin secretion 4. **Insulin resistance** → impaired glucose utilization ### Metabolic Complications (Options A, B, C — All Real) | Complication | Mechanism | Clinical Significance | |---|---|---| | **Hyperglycemia** | Reduced insulin secretion + insulin resistance | Risk of type 2 DM; monitor fasting glucose, HbA1c | | **Dyslipidemia** | Weight gain + direct lipid metabolism effects | ↑ Triglycerides, ↓ HDL; cardiovascular risk | | **Hyponatremia (SIADH)** | Antipsychotics enhance ADH release from posterior pituitary | Mild hyponatremia (125–130 mEq/L) common; rarely symptomatic | | **Weight gain** | H1 antagonism + 5-HT2C antagonism + appetite stimulation | Up to 10–15 kg over 2–3 years | **High-Yield:** SIADH-induced hyponatremia is a recognized (though often mild and asymptomatic) side effect of many antipsychotics, including olanzapine. It occurs within weeks to months of initiation. ### Why Option D Is Wrong Olanzapine does **NOT** cause hyperthyroidism. There is **no evidence** that olanzapine: - Inhibits thyroid peroxidase (TPO) - Enhances thyroid hormone synthesis - Causes Graves' disease or thyroiditis In fact, **hypothyroidism** (not hyperthyroidism) has been rarely reported with some antipsychotics, but it is not a recognized mechanism of olanzapine. The stem's claim of "direct thyroid peroxidase inhibition" leading to hyperthyroidism is physiologically implausible — TPO inhibition would reduce thyroid hormone synthesis, causing *hypo*thyroidism, not hyperthyroidism. **Clinical Pearl:** Thyroid function should be monitored in patients on antipsychotics, but this is to detect hypothyroidism (if it occurs) or to establish baseline before attributing mood symptoms to thyroid disease — not because antipsychotics commonly cause thyroid dysfunction. **Mnemonic for Olanzapine's "Big Three" Metabolic Risks:** **WGD** = Weight Gain, Glucose dysregulation, Dyslipidemia. These are the hallmarks of olanzapine-induced metabolic syndrome. ### Monitoring Recommendations For patients on olanzapine: - Baseline and annual: fasting glucose, lipid panel, weight, waist circumference - Consider switching to aripiprazole or ziprasidone if metabolic syndrome develops - Lifestyle intervention (diet, exercise) is first-line