Symptoms of Hyperthyroidism
Hyperthyroidism presents with a constellation of symptoms affecting multiple body systems, including tachycardia, palpitations, anxiety, heat intolerance, unintentional weight loss, excessive sweating, fatigue, and muscle weakness. 1
Common Clinical Manifestations
Cardiovascular Symptoms
- Tachycardia and palpitations
- Hypertension
- Atrial fibrillation (especially in older patients)
- High-output heart failure in severe cases 1, 2
- Increased cardiac output (up to 300% from euthyroid state) 2
- Pulmonary artery hypertension 2
Neuropsychiatric Symptoms
- Anxiety and nervousness
- Insomnia
- Fine tremor of outstretched hands
- Hyperactivity 1
Metabolic and Constitutional Symptoms
- Unintentional weight loss (despite normal or increased appetite)
- Heat intolerance
- Excessive sweating
- Fatigue
- Muscle weakness 1, 3
- Diarrhea 3
Dermatologic Manifestations
- Warm, moist skin
- Excessive sweating
- Hair loss
- Pretibial myxedema (specific to Graves' disease) 1
Ophthalmologic Signs (particularly in Graves' disease)
Special Considerations
Age-Related Differences
- Older adults may exhibit more subtle symptoms, often limited to cardiovascular manifestations, known as "apathetic hyperthyroidism" 1
- Younger patients typically present with more classic hypermetabolic symptoms 4
Severity Spectrum
- Subclinical hyperthyroidism (low TSH but normal T4 and T3) may present with milder or absent symptoms 1
- Thyroid storm represents the most severe form of thyrotoxicosis, characterized by altered mental status and high mortality if untreated 5
Diagnostic Approach
Laboratory testing is essential for confirming hyperthyroidism when clinical suspicion exists:
Additional testing to determine etiology may include:
- Radioactive iodine uptake and scan
- TSH receptor antibodies (for Graves' disease) 1
Complications of Untreated Hyperthyroidism
If left untreated, hyperthyroidism can lead to serious complications:
- Cardiac arrhythmias (particularly atrial fibrillation)
- Heart failure
- Osteoporosis and increased fracture risk
- Thyroid storm (medical emergency)
- Adverse pregnancy outcomes 1, 3
- Increased all-cause mortality 3
Common Pitfalls in Diagnosis
- Symptoms may mimic other conditions, leading to delayed diagnosis 5
- Muscle weakness may present unilaterally, potentially misleading clinicians toward neurological diagnoses 6
- Beta-blockers can mask certain clinical signs of hyperthyroidism 1
- Older adults may present with predominantly cardiovascular symptoms rather than classic hypermetabolic features 1
The recognition of this constellation of symptoms should prompt appropriate laboratory testing to confirm the diagnosis and initiate timely treatment with antithyroid drugs, radioactive iodine ablation, or surgery, depending on the underlying cause and patient factors 3, 4.