What should be monitored in patients with hypothyroidism who are started on thyroid hormone replacement therapy?

In patients with hypothyroidism who are initiated on thyroid hormone replacement therapy, monitoring TSH (thyroid-stimulating hormone) levels is essential for managing treatment. TSH is produced by the pituitary gland in response to the levels of thyroid hormones (T3 and T4) in the bloodstream. When thyroid hormone therapy commences, the goal is to normalize TSH levels, indicating that the thyroid hormone replacement is adequate and that the body is receiving enough thyroid hormone to meet its needs.

If the TSH level remains high, it suggests that the patient might require a higher dose of thyroid hormone replacement. Conversely, if TSH levels drop too low, it may indicate overtreatment with thyroid hormones, which can lead to adverse effects such as hyperthyroid symptoms.

While T3 levels can provide additional information regarding therapy adequacy, they are less commonly used for monitoring in clinical practice because TSH is generally considered a more reliable marker of thyroid function. Monitoring thyroid antibodies is important in specific cases of autoimmune thyroid disease, but is not necessary for routine management once therapy begins. Blood sugar levels are also unrelated to thyroid hormone replacement and therefore not relevant to monitoring in this context.