Hyperthyroidism is the excessive production of thyroxine due to abnormal functioning of the thyroid gland. In hyperthyroidism the T4 level is high with a low TSH. A low level of TSH with high circulating levels of free T3/T4 is diagnostic of thyrotoxicosis (thyroid storm). Thyrotoxicosis can result from excess intake of exogenous thyroid hormone. In hyperthyroidism there is an increase in metabolic rate, oxygen consumption, use of metabolic fuels, and sympathetic nervous system responsiveness. Graves disease is an autoimmune disorder characterized by abnormal stimulation of the thyroid gland by thyroid-stimulating antibodies that act through the normal TSH receptors. A goiter and ophthalmopathy are usually present in Graves disease. It is associated with human leukocyte antigen (HLA)-DR3 and HLA-B8.
Forms of hyperthyroidism (major forms)
- Graves’ disease (most common)
- Toxic nodular goiter (Plummer’s disease)
- Thyrotoxic Crisis (Thyroid Storm)
Typical symptoms of hyperthyroidism
- Thyroid storm
- Restlessness, irritability, anxiety
- Increased cardiac output
- Tachycardia and palpitations
- Diarrhea, increased appetite
- Heat intolerance, increased sweating
- Thin and silky skin and hair
- Weight loss
- Graves Disease is excessive thyroid hormone secretion (most common cause)
- Most frequently in women 20 to 40 years of age.
- The incidence in females is 6 times greater than in males.
- Surgical removal of thyroid tissue
- Destruction of thyroid tissue with radioactive iodine
- Suppression of thyroid hormone synthesis with Antithyroid drugs
- Radiation is the preferred treatment for adults
- Antithyroid drugs are preferred for younger patients.
- Beta Blockers and nonradioactive iodine may be used as adjunctive therapy. Beta-blockers suppress tachycardia by blocking beta-receptors on the heart.
- Nonradioactive iodine inhibits synthesis and release of thyroid hormones.
Thyroid storm (thyrotoxic crises)
- High fever
- Cardiovascular effects =tachycardia, congestive failure, and angina
- Severe CNS effects =agitation, restlessness, and delirium
- High mortality rate
Treatments for hyperthyroidism
- Antithyroid drugs =inhibit the synthesis of T4 and T3
- Surgical resection =remove hyperplastic and adenomatous tissues and restores normal thyroid function and pituitary function
- Radioactive iodine therapy =iodine 131 is taken up by functioning thyroid tissue and will decrease thyroid hormone production
- Inhibits thyroid hormone synthesis
- Short half-life
- Used in the treatment of Graves disease, thyrotoxic crises, preparation for thyroid gland surgery, and adjunct to radiation therapy
Adverse effects of Propylthiouracil (PTU)
Radioactive Iodine-131 (131I)
- Produces clinical remission with destruction of thyroid gland
- Radioactive isotope of stable iodine
- Emits gamma and beta rays
- Half-life is 8 days
- Used in Graves’ disease
- Contraindicated in pregnancy and lactation
- Strong iodine solution (Lugol’s solution)
- Used to suppress thyroid function in preparation for thyroidectomy
Adverse effects of nonradioactive iodine
- Brassy taste
- Burning sensation in the mouth and throat
- Soreness of the teeth and gums
- Frontal headache
- Various skin eruptions
- A side effect of PTU (propylthiouracil) is agranulocytosis.
- Treatment of graves disease is radioactive iodine therapy.
- A patient with symptoms of tachycardia, nervousness, tremors, restlessness, and weight loss probably has hyperthyroidism.