A 17-year-old girl was evaluated for complaints of weight gain, hair loss, constipation and weakness. Her free T4 level was low and TSH was increased. Which of the following is the most likely diagnosis?

The patient is having symptoms of hypothyroidism and thryoid profile reveals primary hypothyroidism. Analyzing all options, Graves' disease and McCune-Albright syndrome are associated with hypehyroidism. (excludes 'a' & 'b') In pituitary adenoma/TSH-secreting pituitary tumor - increased TSH with increased T3/T4 would be seen. (option 'c' excluded) Primary hypothyroidism is d/t defect in thyroid gland itself; associated with high TSH & low free T4 levels. Hashimoto's thyroiditis is a cause of primary hypothroidism.