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Hypothyroidism affects two out of every thousand women. It affects about 6-10% of women over the age of 65 and about 2-3% of men.
The most common cause of hypothyroidism is Hashimoto's thyroiditis, a chronic autoimmune destruction of the thyroid. Other causes of hypothyroidism include radioactive iodine, thyroidectomy, thioamide drugs, and iodine ingestion. Transient hypothyroidism can occur in patients with acute thyroiditis.
Symptoms. Patients present with cold intolerance, mental slowing, and weight gain. Other symptoms may include constipation, dry skin, menstrual disorders, and muscle cramps.
Physical Examination. Peripheral edema (pitting and non-pitting), bradycardia, cool dry skin, gravelly voice, hypothermia, brittle hair, and delayed relaxation phase of tendon reflexes.
| Differential Diagnosis | ||
Cause |
Clues to Diagnosis |
|
| Autoimmune thyroiditis (Hashimoto's disease) | Family or personal history of autoimmune thyroiditis or goiter | |
| Iatrogenic: Ablation, medication, surgery | History of thyroidectomy, irradiation with iodine 131, or thioamide drug therapy | |
| Diet (high levels of iodine) | Kelp consumption | |
| Subacute thyroiditis (viral) | History of painful thyroid gland or neck pain | |
| Postpartum thyroiditis | Symptoms of followed by 6 months postpartum | |
Thyroid Function Tests
Sensitive TSH assays. Immunoradiometric assays can detect abnormally low or abnormally high TSH levels. A sensitive TSH assay is the test of choice for screening for hypothyroidism.
Assessment of free T4 concentrations with a free T4 index or free T4 assay can confirm the diagnosis.