Proximal Muscle Cramps in Obese Hypertensive Woman with Normal Electrolytes
The most likely cause is primary aldosteronism (hyperaldosteronism), which should be screened immediately with a plasma aldosterone-to-renin ratio. 1
Why Primary Aldosteronism is the Leading Diagnosis
Primary aldosteronism presents with muscle weakness, cramps, and hypokalemia in hypertensive patients, but importantly, potassium can be normal in 25-50% of cases. 1 The International Society of Hypertension specifically lists "muscle weakness/tetany, cramps, arrhythmias" as symptoms suggestive of secondary hypertension due to hypokalemia from primary aldosteronism. 1
Key diagnostic features in this patient:
- Obesity is present in 40% of patients with primary aldosteronism, making this combination highly relevant. 1
- Primary aldosteronism has a prevalence of 8-20% in hypertensive populations, making it the most common endocrine cause of secondary hypertension. 1
- Normal serum potassium does NOT exclude primary aldosteronism—hypokalemia may be absent or intermittent. 1
Immediate Diagnostic Workup
Order a plasma aldosterone-to-renin ratio under standardized conditions as the screening test. 1 Before testing:
- Correct any hypokalemia (even if currently normal, check again)
- Withdraw aldosterone antagonists for 4-6 weeks if the patient is on spironolactone
- Note that ACE inhibitors and ARBs can affect the ratio but don't necessarily need to be stopped for screening 1
If the aldosterone-to-renin ratio is elevated, proceed to confirmatory testing with either oral sodium loading test (measuring 24-hour urine aldosterone) or IV saline infusion test (measuring plasma aldosterone at 4 hours). 1
Obtain an adrenal CT scan if biochemical testing confirms primary aldosteronism, followed by adrenal vein sampling to distinguish unilateral from bilateral disease. 1
Why Other Causes Are Less Likely
Diuretic-induced hypokalemia is excluded because serum potassium is normal and there's no mention of diuretic use. 2 While obesity predisposes to potassium depletion during thiazide therapy, this patient hasn't been started on treatment yet. 2
Hypothyroidism causes proximal muscle weakness but presents with delayed ankle reflexes, cold intolerance, weight gain, and elevated TSH—none of which are mentioned here. 1
Hyperthyroidism causes proximal muscle weakness but presents with weight loss, tremor, heat intolerance, and low TSH—opposite of this patient's obesity. 1
Critical Pitfall to Avoid
Do not dismiss secondary hypertension screening just because electrolytes are normal. 1 The 2020 International Society of Hypertension guidelines explicitly state that screening for secondary hypertension is indicated in adults with resistant hypertension OR when specific clinical features are present—proximal muscle cramps in a newly diagnosed hypertensive patient qualifies. 1
The American College of Cardiology guidelines emphasize that normal potassium does not exclude primary aldosteronism, as normokalemic hyperaldosteronism is increasingly recognized. 1
Additional Considerations
Obstructive sleep apnea should also be considered given the obesity, as it has a 25-50% prevalence in hypertensive populations and can coexist with primary aldosteronism. 1 Screen with the Berlin Questionnaire or Epworth Sleepiness Score and ask about snoring, witnessed apneas, and daytime sleepiness. 1
Pheochromocytoma is less likely (prevalence 0.1-0.6%) and typically presents with paroxysmal hypertension, headaches, sweating, and palpitations—not isolated muscle cramps. 1