Measuring TSH is the most common way to assess thyroid function, and many doctors will prescribe thyroid medications based on TSH alone. When they see that a person’s TSH level is high, most physicians assume that the pituitary is producing extra hormone because the thyroid gland isn’t doing its job. The solution? Giving medication to boost thyroid performance. But numerous other factors come into play. For instance, measuring TSH alone does not convey pituitary function, whether thyroid hormones are working normally throughout the body, or whether an autoimmune disorder is the culprit.