What are the common symptoms and signs of hyperthyroidism?

  1. What are the common symptoms and signs of hyperthyroidism?
    Symptoms: nervousness, anxiety, irritability, insomnia, heat intolerance, sweating, palpitations,
    tremors, weight loss with increased appetite, fatigue, weakness, emotional lability, and diarrhea.
    Signs: enlarged thyroid gland, warm skin, thyroid “stare”/lid lag, exophthalmos, proptosis,
    ophthalmoplegia (Graves disease), pretibial myxedema (Graves disease), tremor, tachycardia,
    and atrial fibrillation. Check thyroid-stimulating hormone (TSH) when patients present with
    new-onset atrial fibrillation.
  2. What are the most common causes of hyperthyroidism?
    The most common cause is Graves disease, which is characterized by a diffusely enlarged
    thyroid gland, positive thyroid-stimulating immunoglobulins and antibodies, exophthalmos,
    proptosis, ophthalmoplegia, and pretibial myxedema. In elderly patients, look for toxic
    multinodular goiter (individual lumps instead of diffuse enlargement of the gland and “hot”
    nodules on thyroid nuclear scan). Other causes include adenoma (single lump that is “hot” on
    nuclear scan), subacute thyroiditis (viral infection with tender, painful thyroid gland), and
    factitious hyperthyroidism (in which the patient takes thyroid hormone). Rare, exotic causes
    include amiodarone (which can cause hypo- or hyperthyroidism), TSH-producing pituitary tumor,
    thyroid carcinoma, and struma ovarii (an ovarian teratoma that secretes thyroid hormone).
  3. Describe the classic laboratory pattern of hyperthyroidism.
    The TSH level is low (unless the patient has a TSH-secreting tumor), whereas triiodothyronine
    (T3) and thyroxine (T4) are increased.
  4. How is hyperthyroidism treated?
    Short-term (stabilizing) treatment: Propylthiouracil (PTU) and methimazole/carbimazole can
    be used as suppressive agents. Beta blockers are used in the setting of thyroid storm
    (severe hyperthyroid state—an emergency). Iodine can also suppress the thyroid gland but is
    rarely used for this purpose clinically.
    Definitive (curative) treatment: Radioactive iodine ablation of the thyroid gland is typically
    used. Surgery is preferred in pregnant patients. Hypothyroidism may result from either
    treatment; if so, it is treated with thyroid hormone replacement (for life).
  5. What are the symptoms and signs of hypothyroidism?
    Symptoms: weakness, lethargy, fatigue, cold intolerance, weight gain with anorexia,
    constipation, loss of hair, hoarseness, menstrual irregularity (menorrhagia is classic), myalgias
    and arthralgias, memory impairment, and dementia. Always rule out hypothyroidism as a
    cause of dementia.
    Signs: bradycardia; dry, coarse, cold, and pale skin; periorbital and peripheral edema;
    coarse, thin hair; thick tongue; slow speech; decreased reflexes; hypertension; carpal tunnel
    syndrome and paresthesias; vitiligo, pernicious anemia, and diabetes (remember the
    autoimmune association between these three conditions and Hashimoto disease); and coma
    (severe disease).
    In children, cretinism may occur (mental, motor, and growth retardation).
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  6. What are the common causes of hypothyroidism?
    The most common known cause is Hashimoto thyroiditis. Women of reproductive age
    outnumber men by 8:1. Histology reveals lymphocytes in the thyroid gland as well as
    antithyroid and antimicrosomal antibodies. Other autoimmune diseases may coexist. The
    associated goiter is nontender. The second most common cause is iatrogenic after treatment
    of hyperthyroidism. Other less common causes include iodine deficiency, amiodarone, lithium,
    and secondary hypothyroidism due to pituitary or hypothalamic failure (look for decreased
    TSH), such as with Sheehan syndrome.
  7. Describe the laboratory findings in hypothyroidism.
    Elevated TSH (unless due to secondary causes), decreased T3 and T4, antithyroid and
    antimicrosomal antibodies (if due to Hashimoto thyroiditis), hypercholesterolemia, and anemia
    (which may be due to chronic disease or coexisting pernicious anemia).
  8. Why is free T4 (or free T4 index) better than total T4 for measuring thyroid
    hormone activity?
    Free T4 (free T4 index) measures the active form of thyroid hormone. Many conditions
    cause a change in the amount of thyroid-binding globulin (TBG), thus changing total T4 levels
    in the absence of hypo- or hyperthyroidism. Common examples include pregnancy, estrogen
    therapy, and oral contraceptive pills, all of which increase TBG. Nephrotic syndrome,
    cirrhosis, and corticosteroid treatment all decrease TBG. T3 resin uptake is an older test that
    is not worth the effort to learn for Step 2, but if you are asked, it should rise or fall in
    the same way as free T4. Although an oversimplification, this principle should serve you well
    on the exam.
  9. How is hypothyroidism treated?
    With T4 or thyroxine. T3 should not be used. In elderly patients, it is important to “start low and
    go slow,” because overtreatment can be dangerous.
  10. What is euthyroid sick syndrome?
    Any patient with any illness may have temporary derangements in thyroid function tests that
    resemble hypothyroidism. TSH ranges from normal to mildly elevated, and serum T4 ranges
    from normal to mildly decreased. Clinical circumstances and physical findings are the best
    guides to whether the patient has true hypothyroidism. In patients with euthyroid sick
    syndrome, simply treat the underlying illness. If the diagnosis is in doubt, either remeasure
    thyroid tests after the patient recovers (preferred) or try an empirical dose of levothyroxine
    (if the patient does not respond to treatment of the underlying illness).