In a client with extreme tachycardia, diarrhea, weight loss, hypertension, and intolerance to heat, which hormone is likely affecting metabolic rate?

• A. Thyroxine (T4)
• B. Antidiuretic hormone (ADH)
• C. Triiodothyronine (T3)
• D. Cortisol

Answer: (C)

The presence of extreme tachycardia, diarrhea, weight loss, hypertension, and intolerance to heat highlights a significant elevation in metabolic rate, commonly associated with hyperthyroidism. Among the hormones listed, triiodothyronine (T3) plays a crucial role in regulating metabolic processes within the body. T3 is the more active form of thyroid hormones, and it directly influences the basal metabolic rate by increasing the rate of metabolism in almost all tissues.

This hormone enhances protein synthesis, increases the rate of glucose uptake, promotes the utilization of fats, and generally accelerates energy expenditure, leading to the symptoms observed in the client. While thyroxine (T4) is another thyroid hormone, it primarily acts as a precursor to T3, with much of its effects being mediated through T3. Thus, when considering direct impacts on metabolic rate, T3 is the key hormone responsible for the symptoms described.

In contrast, antidiuretic hormone (ADH) is primarily involved in regulating water balance and does not have a direct relationship with metabolic rate. Cortisol, while important for numerous metabolic functions such as glucose metabolism, is more associated with stress responses and energy mobilization rather than elevated metabolic rates seen in hyperthyroid conditions.