What is the expected serum total T4 concentration in hypothyroidism?

In hypothyroidism, the expected serum total T4 concentration is indeed decreased. This condition is characterized by an underactive thyroid gland, which does not produce sufficient amounts of thyroid hormones, including thyroxine (T4). The role of T4 is critical as it helps regulate metabolism and energy levels in the body. When thyroid function is impaired, as seen in hypothyroidism, the production of T4 is insufficient, leading to a lower serum concentration.

Furthermore, diagnostic evaluations for hypothyroidism often reveal not only low levels of T4 but also high levels of thyroid-stimulating hormone (TSH) as the pituitary gland attempts to stimulate the underactive thyroid. Monitoring the balance of these hormones is essential in confirming hypothyroidism and managing treatment effectively. The decreased T4 levels in hypothyroidism are a fundamental aspect of understanding thyroid physiology and pathology in clinical practice.