A nurse is caring for a patient with decreased triiodothyronine (T3) and thyroxine (T4) and elevated thyroid-stimulating hormone (TSH) levels. The nurse knows the patient is likely suffering from what?

Choice A reason: Hyperthyroidism involves elevated T3 and T4 with low TSH due to excessive thyroid hormone production. The patient’s low T3/T4 and high TSH indicate reduced thyroid activity, not overactivity, as the pituitary increases TSH to stimulate the underactive thyroid, making this choice incorrect. Choice B reason: Hypothyroidism is characterized by low T3 and T4 levels due to underactive thyroid function, prompting the pituitary to secrete more TSH to stimulate hormone production. This matches the patient’s lab results (low T3/T4, high TSH), often seen in primary hypothyroidism, making this the correct choice. Choice C reason: Thyroid cancer may alter thyroid function but typically doesn’t present with consistently low T3/T4 and high TSH. It’s more likely to cause nodules or abnormal growths, not this specific hormonal pattern, which aligns with hypothyroidism, making this choice less likely. Choice D reason: Pituitary adenoma causing secondary hypothyroidism would lower TSH, T3, and T4 due to impaired pituitary function. High TSH with low T3/T4 suggests primary thyroid failure, not pituitary dysfunction, making this choice incorrect for the patient’s hormonal profile.