Hashimoto's Thyroiditis
Hashimoto's thyroiditis is the most common cause of hypothyroidism in the US, an autoimmune condition treated per the American Thyroid Association (ATA) hypothyroidism treatment guideline.
Symptoms
Fatigue, weight gain, cold intolerance, constipation, dry skin, hair thinning, depression, and irregular periods -- symptoms often develop gradually and can be easy to attribute to other causes.
Causes and risk
An autoimmune attack on the thyroid gland; genetics, other autoimmune conditions, and being female all raise risk.
How it is evaluated
TSH is the first-line test, with reflex free T4 and thyroid antibody testing (anti-TPO) to confirm the autoimmune cause, per AAFP diagnostic guidance.
Treatment
Levothyroxine, taken on an empty stomach, is the standard first-line treatment, with the dose titrated to normalize TSH, per the ATA guideline. Combination T4/T3 therapy and dietary/selenium approaches are less firmly supported by guideline evidence than levothyroxine monotherapy.
When to seek care
Severe, untreated hypothyroidism can progress to myxedema coma -- altered mental status, low body temperature, and a slow heart rate -- which is a medical emergency requiring immediate care, per current JAMA review data. Oral levothyroxine is not adequate treatment for this emergency; it requires IV therapy in a hospital.