In what condition would you expect a patient's TSH levels to be abnormally high?

In primary hypothyroidism, the thyroid gland is unable to produce enough thyroid hormones (like thyroxine, T4, and triiodothyronine, T3) due to intrinsic thyroid gland failure. In response to low levels of thyroid hormones, the pituitary gland produces more thyroid-stimulating hormone (TSH) to stimulate the thyroid gland to increase hormone production. Consequently, in primary hypothyroidism, TSH levels are abnormally high due to the feedback mechanism where low hormone levels trigger increased TSH secretion.

In contrast, conditions like thyrotoxicosis involve excessive production of thyroid hormones, leading to suppressed TSH levels because of the negative feedback to the pituitary gland. Secondary adrenal insufficiency and secondary thyroid disease typically do not involve the primary thyroid hormone production issues found in primary hypothyroidism, hence would not lead to elevated TSH in the same manner. In summary, primary hypothyroidism is characterized by elevated TSH levels as the body attempts to compensate for the insufficient production of thyroid hormones.