Which hormone generally indicates thyroid hormone levels in the body?

The hormone that typically serves as an indicator of thyroid hormone levels in the body is TSH, or thyroid-stimulating hormone. TSH is produced by the pituitary gland and regulates the production of thyroid hormones T3 (triiodothyronine) and T4 (thyroxine) from the thyroid gland. When the levels of thyroid hormones in the blood are low, TSH levels generally increase in response, signaling the thyroid gland to produce more hormones. Conversely, when thyroid hormone levels are adequate or elevated, TSH levels decrease to reduce thyroid hormone production.

T4, although it is a primary hormone produced by the thyroid, serves as an output of the thyroid gland rather than a direct indicator of its function. Instead, TSH levels are more commonly used as a measure for evaluating thyroid function, making it the more accurate indicator in this context.

In summary, TSH correlates with thyroid hormone levels and serves as a regulatory mechanism, making it the most appropriate choice for indicating thyroid hormone status in the body.