Hyperthyroidism

Hyperthyroidism is a state of high circulating thyroid hormones due to overproduction by the thyroid gland or other sources. Thyrotoxicosis is the clinical syndrome that results from excess thyroid hormone with thyroid storm being the most severe form. Thyroid storm, a rare diagnosis, can occur in patients with or without preexisting hyperthyroidism and is usually triggered by factors such as trauma, myocardial infarction, surgery (including thyroid surgery for hyperthyroidism), or infection. Thyroid storm is a medical emergency, warranting immediate administration of medications to block the production and release of thyroid hormone and management of systemic illness (Ross, 2024b).
 
Causes of Hyperthyroidism

• Graves’ Disease
• Thyroid tumor/nodule
• Excessive intake of thyroid hormones
• Abnormal secretion of TSH
• Thyroiditis
• Excessive iodine intake or iodine-containing medications such as amiodarone

Signs and Symptoms of Hyperthyroidism (Ross, 2024c)

• Neck: Goiter (enlarged thyroid) may or may not be present; thyroid gland may or may not be tender
• Skin: warm, sweaty, hyperpigmentation, pruritus, hives, loose and soft nails, thinning or loss of hair
• Eyes: lid lag, exophthalmos, impairment of eye muscles, periorbital and conjunctival edema
• Hematology: immune thrombocytopenia, pernicious anemia, increased prothrombotic factors (factors VIII, IX, fibrinogen, plasminogen activator inhibitor-1)
• Cardiovascular: tachycardia, hypertension, widened pulse pressure, atrial fibrillation
• Respiratory: dyspnea and dyspnea on exertion
• Gastrointestinal: weight loss, increased metabolic rate, vomiting, diarrhea, dysphagia
• Metabolic: bone density loss, osteoporosis, hyperglycemia, low serum cortisol
• Genitourinary: urinary frequency, nocturia
• Reproductive: amenorrhea
• Neuropsychiatric: anxiety, nervousness, restlessness, irritability, emotional lability, insomnia, psychosis, agitation, depression, confusion, poor concentration
• Musculoskeletal: tremors in the hands, weakness
• Heat intolerance
• Goiter (enlarged thyroid)

Treatment of Hyperthyroidism
Hyperthyroid treatment includes the following:

• Medications:
  • Beta-blockers: alleviate symptoms (palpitations, tachycardia, tremors, anxiety)
  • Thionamides (antithyroid drugs): methimazole and propylthiouracil reduce thyroid hormone synthesis; may suppress white blood cell production
• Radioactive iodine: one-time oral treatment ablates the hyperactive gland
  • A major complication of this treatment is permanent hypothyroidism.
• Surgery to remove the thyroid tissue that is producing the excessive thyroid hormone. 
  • A major complication is disruption of the surrounding tissue, including accidental removal of the parathyroid glands, resulting in low calcium levels requiring calcium replacement.

• Monitor vital signs, especially temperature, heart rate, and blood pressure (all increased in hyperthyroidism).
• Monitor for chest pain.
• Obtain ECG for any abnormal rate or rhythm.
• Use antipyretics and a cooling blanket for fever as needed.

Special Populations

Pregnancy
Thyroid dysfunction in pregnancy is associated with preeclampsia, spontaneous abortion, abnormal fetal brain development, and fetal mortality. In general, increased dosage requirements of thyroid replacement medications should be anticipated, especially during first and second trimesters.
             
Children
Thyroid hormones play a critical role in neurologic development in children. Low or absent levels of thyroid hormone may result in cretinism, and neonatal hypothyroidism accounts for the most preventable cause of intellectual disability. 
 
Elderly
Signs and symptoms of hypothyroidism may be very subtle and mistakenly attributed to normal aging changes. Taking a careful history is important to make the correct diagnosis and helps to avoid erroneous diagnoses of heart failure, dementia, or depression.  

Thyroid Function Tests (TFTs) (Ross, 2023)

Thyroid function tests (TFTs) are used to screen thyroid activity. TSH is the gold standard for evaluating thyroid function.

When screening for thyroid dysfunction:
     • If the TSH is normal, no further testing is required.
     • If the TSH is high, check free T4 to determine the degree of hypothyroidism.
     • If the TSH is low, check free T4 and T3 to determine the degree of hyperthyroidism. 
     • If pituitary or hypothalamic disease is suspected, check both serum TSH and free T4.
     • If TSH is normal, but patient has convincing symptoms of thyroid dysfunction, check free T4.

Note: TSH levels peak in the evening and are at their lowest in the afternoon. Also, levels may vary with severe stress, illness, trauma, and low energy intake.