Question

Laboratory assessment of a patient with subclinical hypothyroidism is likely to reveal:

TSH=0.1 mIU/L (0.4-4.0 mIU/L); total T4=7.2 mcg/dL (4.5-12.0 mcg/dL).
TSH=2.6 mIU/L (0.4-4.0 mIU/L); total T3=310 ng/dL (95-190 ng/dL).
TSH=7.7 mIU/L (0.4-4.0 mIU/L); free T4=22 pmol/L (10-27 pmol/L).
TSH=0.2 mIU/L (0.4-4.0 mIU/L); free T3=1.7 ng/dL (0.2-0.5 ng/dL).

Answer 1

In subclinical hypothyroidism, lab results typically show elevated TSH levels and normal free T4 levels, which in this case is TSH=7.7 mIU/L and free T4=22 pmol/L.

Step-by-step explanation:

A patient with subclinical hypothyroidism is likely to have laboratory results showing an elevated Thyroid-Stimulating Hormone (TSH) with a normal range of thyroid hormones (T3 and T4). The correct lab result that indicates subclinical hypothyroidism in the choices provided is TSH=7.7 mIU/L (0.4-4.0 mIU/L); free T4=22 pmol/L (10-27 pmol/L). This answer reflects an increased TSH level above the normal range while the T4 level remains within the normal range. In the regulatory mechanism of thyroid hormones, the hypothalamic-pituitary-thyroid axis plays a critical role.

Low levels of free T4 stimulate the hypothalamus to release thyrotropin-releasing hormone (TRH), which in turn promotes the anterior pituitary to secrete TSH. TSH stimulates the thyroid gland to produce and release T3 and T4. Persistent elevation in TSH indicates that the thyroid gland is not responding adequately to the pituitary signal, which is typical for subclinical hypothyroidism.