After several days of treatment, what laboratory value indicates that Nevaeh's condition is improving?

A TSH level of 2.2 ng/dL suggests that Nevaeh's condition is improving because it falls within the normal reference range for serum thyroid-stimulating hormone (TSH), which typically spans approximately 0.4 to 4.0 ng/dL.

In the context of thyroid function, a decreasing TSH level after treatment indicates a response to therapy, particularly if the patient was previously experiencing elevated TSH levels due to hypothyroidism or an underactive thyroid. A TSH level that normalizes reflects an improvement in the feedback mechanism of the hypothalamic-pituitary-thyroid axis and suggests that the thyroid gland is beginning to function appropriately again, or that exogenous thyroid hormone therapy (if applicable) is effectively managing the condition.

The other values presented indicate either normalcy or potential issues: higher values could suggest persistent hypothyroidism or an inadequate response to treatment, while a very low value might indicate hyperthyroidism or excessive treatment. Thus, the presence of a TSH level in the normal range, as indicated by the 2.2 ng/dL reading, is a strong indication of improvement in Nevaeh's condition.