© 2017 by Nova Science Publishers, Inc. All rights reserved. This chapter evaluates and discusses the rare presentation of a thyrotropin secreting hormone (TSH) secreting adenoma (TSH-oma) in the setting of a patient who had primary hypothyroidism from Hashimoto’s thyroiditis. TSH secreting tumors are quite rare making up less than 1% of all pituitary tumors [1]. TSH producing cells or Thyrotroph cells represent less than 5% of all pituitary cells. This can somewhat explain their rare presentation. The diagnosis of TSH-omas is often later in the course of the disease. Most clinicians have a low suspicion given the rarity of disease and as a result tumors remain undiagnosed until they grow to the size of a macroadenoma or greater than 10 mm [2]. Even when the suspicion is high, the diagnosis of a TSH-oma may be challenging. The patient described here suffers from TSH-oma with coexisting primary hypothyroidism. The diagnosis is confounded by biochemical and clinical discordance that required a high level of suspicion and a systematic approach. This chapter describes in detail the diagnostic challenges, therapeutic interventions and common presentations of a very rare disease.