What could be causing my excessive foot sweating, insomnia, and weight gain?

Differential Diagnosis for Excessive Foot Sweating, Insomnia, and Weight Gain

Your symptom triad of excessive foot sweating, difficulty sleeping, and weight gain should prompt immediate evaluation for secondary causes of hypertension, particularly pheochromocytoma, hyperthyroidism, Cushing's syndrome, and hypothyroidism, as these endocrine disorders can present with this exact constellation of symptoms and have significant morbidity if left untreated.

Priority Endocrine Evaluations

Pheochromocytoma/Paraganglioma (Most Urgent)

• This rare tumor (0.1-0.6% prevalence) classically presents with headache, sweating, palpitations, and pallor—your sweating fits this pattern 1
• The "spells" of sympathetic overactivity can disrupt sleep and cause weight fluctuations 1
• Screen immediately with 24-hour urinary fractionated metanephrines or plasma metanephrines under standardized conditions 1
• If positive, confirm with CT or MRI of abdomen/pelvis 1

Hyperthyroidism

• Presents with warm, moist skin, heat intolerance, nervousness, tremulousness, insomnia, and paradoxically can cause weight loss OR weight gain in some patients 1
• Prevalence <1% but highly treatable 1
• Screen with TSH and free thyroxine 1
• Physical exam shows lid lag, fine tremor of outstretched hands, warm moist skin 1
• Confirm with radioactive iodine uptake and scan if screening positive 1

Cushing's Syndrome

• Classic presentation includes rapid weight gain (especially central distribution), proximal muscle weakness, depression, and hyperglycemia 1
• Prevalence <0.1% but devastating if missed 1
• Look for central obesity, "moon" face, dorsal and supraclavicular fat pads, wide (>1 cm) violaceous striae, hirsutism 1
• Screen with overnight 1-mg dexamethasone suppression test 1
• Confirm with 24-hour urinary free cortisol excretion (preferably multiple collections) or midnight salivary cortisol 1

Hypothyroidism

• Presents with dry skin, cold intolerance, constipation, hoarseness, and weight gain 1
• Prevalence <1% 1
• Physical exam shows delayed ankle reflex, periorbital puffiness, coarse skin, cold skin, slow movement, goiter 1
• Screen with TSH and free thyroxine 1
• No confirmatory test needed if screening positive 1

Sleep Disorder Considerations

Obstructive Sleep Apnea

• Prevalence 25-50% in hypertensive patients; presents with snoring, fitful sleep, breathing pauses, daytime sleepiness 1
• Associated with obesity and loss of normal nocturnal blood pressure fall 1
• Nocturnal hyperhidrosis is a recognized feature of OSA due to sympathetic overactivity 2
• Screen with Berlin Questionnaire, Epworth Sleepiness Score, overnight oximetry 1
• Confirm with polysomnography 1

Primary Insomnia and Weight Gain

• Sleep problems, particularly trouble falling asleep, waking several times per night, and trouble staying asleep, are independently associated with major weight gain (≥5 kg) in women 3
• The association persists after adjusting for baseline BMI, physical health, health behaviors, and common mental disorders 3
• Weight gain exceeding 2.06 kg/m² increases risk of developing difficulty maintaining sleep (OR 1.58), excessive daytime sleepiness (OR 2.25), and insomnia (OR 2.78) 4

Drug-Induced Causes

Medications and Substances

• Prevalence 2-4%; multiple agents cause this triad including sympathomimetics (decongestants, anorectics), cocaine, amphetamines, caffeine, nicotine, alcohol, NSAIDs, oral contraceptives 1
• Physical exam may show fine tremor, tachycardia, sweating with stimulants 1
• Obtain urinary drug screen for illicit drugs 1
• Diagnosis confirmed by response to withdrawal of suspected agent 1

Recommended Diagnostic Algorithm

1. Obtain detailed medication/substance history first (most common reversible cause) 1
2. Screen all patients with TSH and free thyroxine (simple, inexpensive, high yield) 1
3. If sweating is episodic with "spells," obtain 24-hour urinary fractionated metanephrines (pheochromocytoma can be fatal if missed) 1
4. If rapid central weight gain with cushingoid features, perform overnight dexamethasone suppression test 1
5. Assess for sleep apnea with Berlin Questionnaire and Epworth Sleepiness Score 1
6. Consider polysomnography if OSA suspected 1

Critical Pitfalls to Avoid

• Do not attribute all symptoms to "stress" or "poor sleep hygiene" without excluding secondary causes 1
• Foot-specific sweating (plantar hyperhidrosis) can indicate autonomic neuropathy in diabetes—check fasting glucose and HbA1c 1
• Insomnia with short sleep duration has stronger associations with obesity than insomnia alone 5
• Many antidepressants and antipsychotics used to treat insomnia cause weight gain, creating a vicious cycle 5
• The bidirectional relationship between sleep problems and weight gain means both require simultaneous attention 3, 4