Ace the 2026 RN Endocrine Exam – Empower Your Nursing Journey!

The Thyroid Stimulating Hormone (TSH) test is the standard and most sensitive laboratory test used to diagnose hypothyroidism. TSH is produced by the pituitary gland and is responsible for stimulating the thyroid gland to produce thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3).

In cases of hypothyroidism, where the thyroid is underactive and not producing sufficient amounts of thyroid hormones, the pituitary gland responds by releasing more TSH in an attempt to stimulate the thyroid. Therefore, elevated levels of TSH indicate that the thyroid is not responding adequately, which is a hallmark of hypothyroidism.

While the free thyroxine (T4) test (mentioned as an alternative option) can also provide information about thyroid function, the TSH test is generally the preferred initial test due to its sensitivity and reliability in detecting changes in thyroid function early.

Cortisol level tests and serum potassium levels are unrelated to the diagnosis of hypothyroidism, as they measure different aspects of endocrine function. Cortisol tests are primarily used to evaluate adrenal function, while serum potassium levels relate to fluid and electrolyte balance rather than thyroid activity. Thus, TSH testing is a cornerstone in the