In hypothyroidism the thyroid gland makes too little thyroid hormone, so the body's metabolism slows down. In the US the most common cause is Hashimoto thyroiditis, an autoimmune disease that is more frequent in women.
Key symptoms
- Fatigue and slowed thinking
- Feeling cold and weight gain
- Constipation
- Dry skin, hair loss, heavy periods
- Low mood
What you find on exam
- Slow heart rate
- Dry, coarse skin and a puffy face
- Goiter, or a small, firm thyroid
- Slow relaxation phase of the ankle reflexes
- Swelling that does not pit
Tests
- TSH first: high in primary hypothyroidism
- Free T4: low in overt disease, normal in subclinical disease
- Thyroid peroxidase antibodies to support Hashimoto
- Lipids, sodium and blood count may be abnormal
Treatment basics
- Levothyroxine once a day on an empty stomach
- Lower starting dose in older adults and in heart disease
- Recheck TSH 6 to 8 weeks after each dose change
- Teach: lifelong treatment, take it apart from iron and calcium
Red flags
- Confusion, low temperature and slow breathing: myxedema coma
- Very slow heart rate or low blood pressure
- Chest pain after starting levothyroxine
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Sources: NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations; AAMC Core Entrustable Professional Activities (Core EPAs). Written by Making Synapses. Making Synapses is not affiliated with these organizations.