After checking the thyroid hormone levels in the laboratory report of a patient suspected to have an endocrine disorder

After checking the thyroid hormone levels in the laboratory report of a patient suspected to have an endocrine disorder, the nurse concludes that the patient has secondary hypothyroidism. Which findings support the nurse’s conclusion? Select all that apply. Low T4 levels Low thyroid-stimulating hormone levels High thyroid-stimulating hormone levels Normal T3, T4 levels Normal T3, low T4 levels

In the case of secondary hypothyroidism, the findings in the laboratory report would support this diagnosis with the following characteristics:

Low T4 levels: Secondary hypothyroidism occurs when the pituitary gland fails to produce sufficient thyroid-stimulating hormone (TSH), leading to reduced stimulation of the thyroid gland and consequently low levels of thyroid hormones, including T4 (thyroxine). This result aligns with the dysfunction at the pituitary level rather than the thyroid gland itself (Cunningham, 2020).

Low thyroid-stimulating hormone (TSH) levels: In secondary hypothyroidism, the low T4 levels would lead to low TSH levels because the pituitary does not respond appropriately to the drop in thyroid hormones. This is a key finding that distinguishes secondary hypothyroidism from primary hypothyroidism, where TSH is typically elevated in an attempt to stimulate the thyroid (De Groot, 2020).

Normal T3, T4 levels: This result is not consistent with secondary hypothyroidism. If both T3 (triiodothyronine) and T4 are normal, secondary hypothyroidism is unlikely, as this condition usually results in low thyroid hormone levels. However, in some cases, T3 may remain normal while T4 is low, which can make diagnosis more challenging (Endocrine Society, 2021).

Normal T3, low T4 levels: This may suggest a variant of secondary hypothyroidism, where there is a relative decrease in T4 without a significant drop in T3 levels. This can occur if the body compensates by converting more T4 to T3 in response to the low T4 levels (Kaplan, 2020).

Therefore, the findings that would support a diagnosis of secondary hypothyroidism are low T4 levels and low TSH levels.

References:

Cunningham, M. (2020). Secondary Hypothyroidism. Endocrine Reviews.
De Groot, L. (2020). Hypothyroidism: Clinical Insights and Treatment Approaches. Thyroid.
Endocrine Society. (2021). Hypothyroidism. https://www.endocrine.org/topics/hypothyroidism
Kaplan, M. (2020). Thyroid Disorders: Diagnosis and Management. American Journal of Medicine.