Laboratory report: elevated serum free t4; low serum TSH level. Which of the following is the MOST likely diagnosis?
- Primary hypothyroidism
- Secondary hypothyroidism
- T3 thyrotoxicosis
- Graves disease
- Chronic Hashimoto's thyroiditis
High T4 (hyperthyroid), with a low TSH, indicates that the pituitary is working normally, and the thyroid is hyperactive i.e. Grave's disease. Primary hypothyroidism (Hashimoto's) is low T4 with a high TSH. Secondary hypothyroidism (from pituitary disease) is a low T4 with a low TSH.