In a patient with hypothyroidism, which laboratory finding would you expect?

In a patient with hypothyroidism, elevated TSH (thyroid-stimulating hormone) levels are a key laboratory finding. Hypothyroidism leads to insufficient production of thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3). When these hormones are low, the pituitary gland responds by producing more TSH in an attempt to stimulate the thyroid gland to produce more thyroid hormones.

Therefore, in the context of hypothyroidism, elevated TSH levels serve as a compensatory mechanism highlighting the impaired thyroid function. This is a hallmark of primary hypothyroidism, where a primary defect in the thyroid gland leads to decreased hormone output and subsequently increased stimulation from the pituitary through TSH.

Low T4 and other related factors may also be present, but the elevated TSH is critical in the diagnosis and is typically the most significant indicator in this scenario. This means monitoring TSH is essential in managing and diagnosing hypothyroidism.