In a 6-week-old infant who is sleepy and has not passed stools, what lab result would you expect in a case of congenital hypothyroidism?

In a 6-week-old infant who is sleepy and has not passed stools, what lab result would you expect in a case of congenital hypothyroidism?

• A. High TSH, low T4
• B. Low TSH, high T4
• C. Normal TSH, normal T4
• D. High TSH, normal T4

Answer: (A)

In the context of congenital hypothyroidism, the expected laboratory findings typically include high levels of Thyroid Stimulating Hormone (TSH) and low levels of thyroxine (T4). This condition arises due to an underdeveloped or absent thyroid gland, leading to insufficient production of thyroid hormones. When the body senses low levels of T4, the pituitary gland increases the secretion of TSH in an attempt to stimulate the thyroid gland to produce more T4. In congenital hypothyroidism, however, this feedback system is disrupted because the thyroid is not functioning properly. As a result, despite high TSH levels, T4 remains low. The other potential answers can be ruled out based on the understanding of hypothyroidism. For instance, low TSH and high T4 would indicate hyperthyroidism, while normal TSH and normal T4 would suggest healthy thyroid function. High TSH with a normal T4 level is consistent with secondary causes of hypothyroidism, but in the case of congenital hypothyroidism, the T4 is low. Therefore, the hallmark laboratory findings are indeed high TSH and low T4, making the first option the correct answer.

In the context of congenital hypothyroidism, the expected laboratory findings typically include high levels of Thyroid Stimulating Hormone (TSH) and low levels of thyroxine (T4). This condition arises due to an underdeveloped or absent thyroid gland, leading to insufficient production of thyroid hormones.

When the body senses low levels of T4, the pituitary gland increases the secretion of TSH in an attempt to stimulate the thyroid gland to produce more T4. In congenital hypothyroidism, however, this feedback system is disrupted because the thyroid is not functioning properly. As a result, despite high TSH levels, T4 remains low.

The other potential answers can be ruled out based on the understanding of hypothyroidism. For instance, low TSH and high T4 would indicate hyperthyroidism, while normal TSH and normal T4 would suggest healthy thyroid function. High TSH with a normal T4 level is consistent with secondary causes of hypothyroidism, but in the case of congenital hypothyroidism, the T4 is low. Therefore, the hallmark laboratory findings are indeed high TSH and low T4, making the first option the correct answer.