Final answer:
In hypothyroidism, one would expect to find an increased serum thyroid-stimulating hormone (TSH) due to an underactive thyroid gland not producing enough T3 and T4, despite symptoms of weight gain, cold sensitivity, and fatigue indicating a low metabolism.
Step-by-step explanation:
Hypothyroidism and Serum Hormone Levels In hypothyroidism, one would expect to find an increase in serum thyroid-stimulating hormone (TSH) because the underactive thyroid gland does not produce sufficient amounts of T3 and T4. Consequently, the pituitary gland releases more TSH to stimulate the thyroid. However, since the thyroid gland is not functioning properly, the serum free T4 and total T4 concentration are not increased; they are either normal or decreased. Instead, hypothyroidism is characterized by symptoms such as weight gain, cold sensitivity, low heart rate, and fatigue. In contrast, Patient A's symptoms indicate hypothyroidism, while Patient B's symptoms suggest hyperthyroidism, where there is an overactive thyroid gland. Goiter, which is commonly caused by iodine deficiency, also causes the thyroid gland to struggle in producing T3 and T4, leading to increased production of TSH. In response to low T3 and T4 levels, one would expect symptoms of hypothyroidism, including weight gain, cold sensitivity, and reduced mental activity.
Regarding the options provided:
- Serum free T4 is increased (Incorrect)
- Serum total T4 concentration is increased (Incorrect)
- Serum thyroid-stimulating hormone (TSH) is increased (Correct)
- Serum T3 uptake is increased (Irrelevant to hypothyroidism)
- Serum T3-T4 ratio is decreased (May or may not be relevant depending on other factors)