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Hyperthyroidism
Aka: Hyperthyroidism, Thyrotoxicosis
- See Also
- Subclinical Hyperthyroidism
- Grave's Disease
- Thyroid Storm
- Hyperthyroidism in Pregnancy
- Epidemiology
- Prevalence Overt Hyperthyroidism (US): 0.5% (Subclinical Hyperthyroidism in another 0.7%)
- Women: 2%
- Men 0.2%
- References
- Turnbridge (1977) Clin Endocrinol 7:481-93 [PubMed]
- Pathophysiology
- Excessive Thyroid hormone up-regulates beta-Adrenergic Receptors, increasing sensitivity to Catecholamines
- Causes
- Stimulatory Causes (positive Radioactive Iodine scan)
- Grave's Disease (60-80% of Hyperthyroidism cases)
- Rare
- Trophoblastic Tumors activate TSH receptors via HCG (Choriocarcinoma)
- TSH-secreting Pituitary Adenoma
- Non-Stimulatory Causes
- Toxic Multinodular Goiter (5%, esp. elderly in Iodine deficient regions)
- Toxic Thyroid Adenoma (Plummer's Disease)
- Exogenous Thyroid hormone source
- Thyroiditis (common)
- Subacute Thyroiditis
- Acute Thyroiditis (Bacterial Infection)
- Postpartum Thyroiditis (lymphocytic Thyroiditis)
- Tumors (rare)
- Metastatic follicular Thyroid Cancer
- Ovarian Cancer producing Thyroxine (struma ovarii)
- Medication-Induced Hyperthyroidism
- See Medications Affecting Thyroid Function
- Combined Stimulatory and Non-Stimulatory Causes (positive Radioactive Iodine scan)
- Nodular Goiter with superimposed stimulation
- Symptoms
- Neurologic and psychiatric symptoms
- Nervousness or alertness
- Emotional lability (Anxiety, Irritability or even Psychosis)
- Proximal Muscle Weakness
- Insomnia
- Adrenergic symptoms
- Palpitations
- Tremor
- Frequent Bowel Movements, Diarrhea
- Excessive Sweating
- Heat intolerance
- Miscellaneous
- Weight loss despite increased appetite (hypermetabolism)
- Oligomenorrhea or Amenorrhea
- Signs
- Anxious, restless, fidgeting patient
- Dermatologic
- Warm, moist and velvety
- Palmar erythema
- Hair fine and silky
- Fingernails
- Onycholysis (Plummer's Nails)
- Brown Nail Discoloration
- Graves Dermopathy
- Pretibial Myxedema (Thyroid dermopathy) occurs in 1.5% of cases
- Thyroid Acropachy (hand soft tissue swelling and Digital Clubbing)
- Skin Pigment Changes (patchy Hyperpigmentation or vitilgo)
- Neuromuscular
- Fine Tremor of fingers, Tongue
- Hyperkinesia
- Rapid speech
- Proximal Muscle Weakness (e.g. Quadriceps weakness)
- Eye changes
- See Thyroid Eye Disease
- Stare
- Widened palpebral fissures
- Infrequent blinking
- Chemosis
- Lid lag
- Proptosis (Exophthalmos) - Graves Disease
- Periorbital edema
- Cardiovascular
- Increased Blood Pressure and Heart Rate
- Systolic Hypertension
- Wide Pulse Pressure
- Tachycardia
- Auscultation
- Loud S1 Heart Sound
- Loud S2 Heart Sound
- Systolic Murmur
- Chronic changes
- Atrial Fibrillation (10-15%)
- Cardiac hypertrophy or Cardiomyopathy (5%)
- Labs
- Thyroid testing
- See Thyroid Function Testing
- Obtain Thyroid Stimulating Hormone (TSH) with reflex to Free T4
- Serum Thyroid Stimulating Hormone (TSH) suppressed
- Serum Free Thyroxine (Free T4) elevated
- Normal findings despite abnormal labs
- Pregnancy or Estrogen therapy
- Estrogen increases Thyroxine Binding Globulin and, in turn, Total T4 and Total T3
- TSH and Free T4 will be normal and requires no management
- Acute illness
- TSH mildly decreased (0.1 to 0.4 mIU/ml)
- Normal or mildly decreased Free T4
- Resolves as acute illness does and requires no management
- Exogenous Corticosteroids or Dopamine (e.g. ICU) may cause a similar finding
- Advanced labs: Thyroid Antibodies (indicated in some cases)
- Thyroid Stimulating Immunoglobulin (TSH receptor ab)
- Specific to Graves Disease
- Associated with ophthalmopathy
- Usually not needed for diagnosis unless imaging contraindicated
- Antithyroid Peroxidase Antibody
- Negative in Graves Disease and positive in Hashimoto's Thyroiditis
- Non-specific lab changes (variably present)
- Complete Blood Count (CBC)
- Anemia
- Granulocytosis and Lymphocytosis
- Electrolytes
- Hypercalcemia
- Liver Function Tests
- Liver transaminases (AST,ALT) increased
- Alkaline Phosphatase increased
- Diagnostics
- Thyroid Uptake Scan
- Differentiate Hyperthyroidism causes
- Identify hot and cold Nodules
- Thyroid Ultrasound
- Differentiate solid from cystic Nodules
- May be used when Thyroid uptake scan cannot be used (e.g. pregnancy and Lactation)
- If solid cold Nodule:
- Fine needle biopsy
- CT Head and Neck (evaluate for metastatic disease)
- Evaluation
- Step 1: Check TSH
- TSH Normal
- No Hyperthyroidism
- TSH Suppressed
- Go to Step 2 below
- TSH Increased: Check Free T4
- Normal or Low
- Consider Hypothyroidism
- Free T4 High
- Secondary Hyperthyroidism (rare)
- Obtain CT or MRI Brain with cone down of Pituitary Gland (sella turcica)
- Step 2: Check Free T4 (for suppressed TSH)
- Free T4 High: Go to Step 3
- Free T4 Normal: Measure serum Free T3
- Normal T3
- Follow for transient cause resolution
- Free T3 high
- Go to Step 3
- T3 toxicosis (seen in 10-15% cases)
- Step 3: Thyroid Uptake Scan (Primary Hyperthyroidism)
- Thyroid Uptake Scan with low uptake
- Single "Cold" Nodule
- Possible Thyroid Cancer
- Diffusely low uptake
- Go to Step 4
- Thyroid Uptake Scan with high uptake
- Diffusely high uptake
- Grave's Disease
- Single "Hot" Nodule
- Toxic Thyroid Adenoma
- Multiple "Hot" Nodules
- Toxic Multinodular Goiter
- Step 4: Check Thyroglobulin (scan with low uptake)
- Thyroglobulin Low
- Exogenous hormone source
- Thyroglobulin High
- Thyroiditis
- Ectopic Thyroid hormone production (e.g. ovary)
- Excess iodide exposure
- Management
- See Hyperthyroidism Management
- Complications
- Thyroid Storm
- References
- Bahn (2011) Thyroid 21(6):593-646 [PubMed]
- Haddard (1998) Postgrad Med 104(1):42-59 [PubMed]
- Hennessey (1996) Am Fam Physician 54(4):1315-24 [PubMed]
- Kravets (2016) Am Fam Physician 93(5): 363-70 [PubMed]
- Reid (2005) Am Fam Physician 72:623-36 [PubMed]
- Singer (1995) JAMA 273(10):808-12 [PubMed]
- Slatosky (2000) Am Fam Physician 61(4):1047-52 [PubMed]