en Hematology Hematology case report case report <span style="font-size:14px;"><span style="font-family:Times New Roman;"><span style="line-height:15.0pt"><b><i><span style="color:blue">Background:</span></i></b> This case of pancytopenia due to hypothyroidism and B12 deficiency is rare and severe as a reminder that, upon diagnosis of pancytopenia, endocrine disorders such as secondary thyroid hormone deficiency may need to be considered as a potential cause. </span><br> <span style="line-height:15.0pt"><b><i><span style="color:blue">Case Presentation:</span></i></b><span style="color:black"> A 38-year-old male presented with progressive weakness, lethargy, and anorexia. Initial labs revealed severe pancytopenia, prompting a hematological workup. Bone marrow aspiration ruled out acute leukemia. Further investigations identified severe primary hypothyroidism (TSH: 200 mIU/L) and vitamin B12 deficiency as the underlying causes, after excluding other common etiologies. Treatment with levothyroxine and vitamin B12 was initiated. The patient showed a rapid and significant hematological response, with all cell lines improving and approaching normal ranges on follow-up, confirming the diagnosis.</span><span style="background:lime"></span></span><br> <span style="line-height:15.0pt"><b><i><span style="color:blue">Conclusion:</span></i></b><b> </b><span style="color:black">In this patient, after the diagnosis of hypothyroidism and receiving levothyroxine, we saw a better stability of the improvement of the patient&rsquo;s symptoms and a further improvement in the number of any blood cell lines chiefly platelet which is one of the regulators of the coagulation pathway, and its deficiency increase the risk of bleeding.</span><span style="color:black"></span></span></span></span><br> &nbsp; pancytopenia, anemia, hypothyroidism, levothyroxine, vitamin b12 801 806 http://caspjim.com/browse.php?a_code=A-10-3379-1&slc_lang=en&sid=1 Fatemeh karimpour F.karimpour56@yahoo.com 100319475328460055032 100319475328460055032 Yes Cancer Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran mohammadreza valizadeh mohammadreza14mv@gmail.com 100319475328460055033 0009-0003-2906-1667 No Student research Committee, Babol University of Medical Sciences, Babol, Iran Hanieh Ranjbar haniehranjbar79@gmail.com 100319475328460055034 100319475328460055034 No Student research Committee, Babol University of Medical Sciences, Babol, Iran Zeinab Vosough vosoughz@gmail.com 100319475328460055035 100319475328460055035 No Dept. of Pathology, School of medicine, Babol University of Medical Sciences, Babol, Iran