RATIONALE: Slipped capital femoral epiphysis (SCFE) is a common adolescent hip disorder, but its association with hypothyroidism remains rare and poorly understood. This case highlights the importance of considering endocrine disorders, such as hypothyroidism, as potential risk factors in atypical SCFE presentations, particularly when trauma or other common etiologies are absent. PATIENT CONCERNS: A 14-year-old boy presented with progressive, nontraumatic left hip pain that worsened over 6 weeks, eventually leading to complete immobility. Initially managed unsuccessfully with traditional Chinese medicine, the patient sought care at a trauma center before referral to our hospital. DIAGNOSES: Imaging confirmed a delayed, moderate SCFE of the left hip, characterized by posteromedial displacement of the femoral epiphysis. Laboratory tests revealed significant hypothyroidism, with elevated thyroid-stimulating hormone (>
100 μIU/mL) and reduced thyroid hormone levels (FT4, FT3, TT3, TT4). INTERVENTIONS: The patient underwent open reduction and internal fixation using 4 Kirschner wires via an anterolateral approach, followed by immobilization in a hip spica cast for 2 months. Postoperatively, hypothyroidism was managed with levothyroxine (50 μg/day) under endocrinological supervision. OUTCOMES: After 2 years of follow-up, the patient achieved full functional recovery with no evidence of complications, such as avascular necrosis or residual deformity. Bone union was complete by 8 weeks, and normal activity resumed within 5.5 months. LESSONS: This case underscores the need to screen for thyroid dysfunction in pediatric SCFE patients lacking typical risk factors, such as trauma or obesity. Early recognition and interdisciplinary management of both orthopedic and endocrine aspects can optimize outcomes and prevent long-term complications, emphasizing the value of a comprehensive diagnostic approach.