What does a high TSH and normal T4 mean in a thyroid function test?

A high TSH with normal T4 levels indicates subclinical hypothyroidism, a mild form of thyroid dysfunction where the thyroid gland is underactive but still produces enough T4 to keep levels within the normal range. Symptoms of hypothyroidism may be minimal or absent in this stage, but there is an increased risk of progression to full-blown hypothyroidism if left untreated. Your doctor may recommend monitoring your thyroid function over time and suggest treatment if TSH levels continue to rise or if symptoms appear.