Prealbumin, a multifunctional protein synthesized primarily in the liver, serves as a critical biomarker in clinical practice, offering insights into nutritional status and prognostic outcomes. While its precise physiological role remains incompletely understood, prealbumin is known to facilitate hormone transport, particularly of thyroxine, and contribute to neuroprotection. Clinically, prealbumin levels are sensitive indicators of recent changes in protein intake and absorption, making them invaluable in guiding therapeutic interventions. Alterations in prealbumin levels have been associated with various medical conditions, including chronic kidney disease, liver disease, and cancer, emphasizing its prognostic significance across diverse clinical contexts. we report a case of a 42-year-old male with bipolar disorder managed on lithium therapy, presenting with depressive symptoms and unexpected hyperprealbuminemia. Subsequent investigation revealed primary hypothyroidism secondary to lithium intoxication, highlighting the intricate relationship between lithium therapy, prealbumin levels, and thyroid dysfunction. We discuss the mechanisms and clinical implications of lithium-induced hypothyroidism, emphasizing the importance of considering thyroid function in patients with elevated prealbumin levels. This case underscores the necessity for vigilant monitoring and timely intervention to optimize patient outcomes in cases of lithium-induced thyroid dysfunction. Continued research is crucial for elucidating the complex interactions between prealbumin, lithium therapy, and thyroid function, enhancing our understanding and management of these metabolic disturbances.