A 52-year-old client reports weight gain and tiredness. On assessment, her vital signs are blood pressure 124/74 mm/hg, pulse rate 52 beats/min. respiratory rate 20 breaths/minute, and temperature 98.0 F. Laboratory results show low thyroxine (T4) and triiodothyronine (T3) levels. The nurse knows these symptoms are associated with which condition?

A. Hypothyroidism: Low levels of T4 and T3, combined with symptoms like weight gain, tiredness, and bradycardia, are consistent with hypothyroidism. Hypothyroidism results from an underactive thyroid gland, which produces insufficient thyroid hormones, leading to metabolic slowing and the symptoms described. B. Hyperthyroidism: Hyperthyroidism is associated with high levels of thyroid hormones (T4 and T3), which leads to symptoms like weight loss, tachycardia (fast heart rate), nervousness, and heat intolerance, none of which are present in this client. C. Hypokalemia: Hypokalemia (low potassium levels) typically presents with symptoms such as muscle weakness, fatigue, and cramping, but it does not explain the low thyroid hormone levels or the other signs observed in this case. D. Tetany: Tetany is caused by hypocalcemia (low calcium levels) and is characterized by muscle spasms and tingling sensations. It is not associated with low thyroid hormone levels.