Purpose: Normal or elevated thyrotropin (TSH) levels in the presence of elevated thyroxine is defined as syndrome of inappropriate secretion of TSH. The two main clinical conditions that can lead to this syndrome are TSH-secreting adenoma (TSHoma) and resistance to thyroid hormone. Establishing the correct diagnosis is crucial in order to decide on the most appropriate treatment option. Herein, we present the data of seven patients who were hospitalized for the differential diagnosis of the two clinical entities. Material and Method: Our database was reviewed for patients diagnosed with syndrome of inappropriate secretion of TSH in our hospital between 2010 and 2014. After exclusion of the other rare causes, seven patients who were hospitalized for the differential diagnosis of TSHoma and resistance to thyroid hormone were included. Results: The final diagnosis was resistance to thyroid hormone in four patients, TSHoma in two and equivocal in one. Two patients diagnosed with TSHoma were operated and had positive staining with TSH. Both of the TSHoma cases had macroadenoma on pituitary magnetic resonance imaging and visual field defect, while two of four patients with resistance to thyroid hormone had microadenoma. Alpha-subunit/TSH molar ratio was above 1 in all patients diagnosed with TSHoma while it exceeded 1 in two patients with the final diagnosis of resistance to thyroid hormone. Thyrotrophin-releasing hormone stimulation test revealed a blunted response in all patients with TSHoma and a positive response in all with resistance to thyroid hormone. Discussion: Differential diagnosis of resistance to thyroid hormone and TSHoma can be a clinical challenge and requires complex hormone testing and imaging methods. Since incidental pituitary tumors are not rare, presence of an adenoma should not rule out the diagnosis of resistance to thyroid hormone.Amaç: Bir hastada artmış serum serbest tiroksin varlığında normal veya yüksek tirotropin (TSH) düzeyi uygunsuz TSH sendromu olarak adlandırılır. Bu sendroma yol açabilecek iki önemli hastalık; TSH sekrete eden hipofiz adenomu (TSHoma) ve tiroid hormon direncidir. Ayırıcı tanıyı doğru yapmak, en uygun tedavi seçeneğini belirlemek açısından önemlidir. Burada hospitalize edilerek iki klinik antitenin ayırıcı tanısı yapılan yedi hasta sunulmuştur. Gereç ve Yöntem: 2010-2014 yılları arasında uygunsuz TSH tanısı ile takip edilen hastaların verileri gözden geçirildi. Bulgular: Yedi hastanın dördünde kesin klinik tanı tiroid hormon direnci, iki hastada TSHomaydı. Bir hastada klinik tanı netleştirilemedi. TSHoma tanısı ile takip edilen iki hastada opere oldu ve adenom TSH ile pozitif boyandı. TSHoma olgularının her ikisinde de makroadenom ve görme alanı defekti saptanırken, tiroid hormon direnci olgularının ikisinde de mikroadenom tespit edildi. Alpha-subunit/TSH molar oranı TSHomalı hastaların tümünde ve dirençli hastaların ikisinde birin üzerinde saptandı. Tüm tiroid hormon direnci tanısı konulan hastalarda tirotropin serbestleştirici hormon uyarısına pozitif TSH yanıtı mev...