American Nurses Credentialing Center (ANCC) Practice Exam

In a patient with hypothyroidism who is not taking levothyroxine as prescribed, the expected lab results would indeed show a decreased T4 (thyroxine) level and an increased TSH (thyroid-stimulating hormone) level.

When the thyroid hormone levels, particularly T4, are low due to insufficient treatment, the feedback mechanism to the pituitary gland causes an increase in TSH production. TSH stimulates the thyroid gland to produce more T4, but if the patient is not receiving levothyroxine, the thyroid gland cannot compensate adequately, leading to the persistently low T4 levels. This results in the thyroid function being characterized by low hormone levels (T4) and high TSH levels, indicating that the body is signaling for more thyroid hormone production due to inadequate levels circulating in the bloodstream.

Understanding this relationship between T4 and TSH is fundamental in interpreting thyroid function tests and managing patients with thyroid disorders effectively.