Hypothyroidism & Hashimoto's

What it is

The thyroid sets the body's metabolic pace. In hypothyroidism it makes too little hormone. Where iodine intake is adequate, the most common cause is Hashimoto's thyroiditis, an autoimmune condition that slowly damages the gland.

Symptoms

• Fatigue and slowed thinking

• Feeling cold

• Weight gain and constipation

• Dry skin and thinning hair

• Heavier periods and low mood

How it's diagnosed

A high TSH with low free T4 is overt hypothyroidism; a high TSH with normal free T4 is subclinical. Positive TPO antibodies point to Hashimoto's and a higher chance of progression.

Treatment

Levothyroxine once daily on an empty stomach, separated from calcium, iron and some antacids. TSH is rechecked 6 to 8 weeks after any dose change. Routine combination T4 and T3 therapy is not recommended, though a trial may be considered for people who remain symptomatic despite a normal TSH. Desiccated thyroid extract is not recommended as first-line therapy.

Clinical pearls

• People on levothyroxine usually need a higher dose as soon as pregnancy is confirmed.

• The 2026 ATA pregnancy guideline advises against levothyroxine for euthyroid TPO-positive women.

• Biotin supplements can distort thyroid lab results.