This observational, case-control study will evaluate differences in serum uric acid and related hematologic and biochemical parameters between adolescents (12-18 years) with primary headache and age-/sex-matched controls without recurrent headaches or chronic medical/psychiatric disorders. Cases will meet International Classification of Headache Disorders, 3rd edition (ICHD-3) criteria verified by a pediatric neurologist after comprehensive clinical assessment. The study will also collect sociodemographic data and anthropometrics to calculate BMI. Primary outcome is the between-group difference in serum uric acid levels at enrollment. Secondary outcomes include group differences in ferritin, creatinine, BUN, complete blood count indices (Hb, WBC, neutrophils, lymphocytes, platelets, MPV), and BMI.

Inclusion Criteria:

• Inclusion Criteria (Cases):

Adolescents aged 12-18 years presenting to pediatric neurology outpatient clinics

Diagnosis of primary headache according to the International Classification of Headache Disorders, 3rd edition (ICHD-3) (e.g., 1.1, 1.2, etc.)

Diagnosis confirmed by a pediatric neurologist following a comprehensive clinical evaluation

Sufficient cognitive ability to understand and complete study instruments

• Inclusion Criteria (Controls):

Adolescents aged 12-18 years presenting to general pediatric outpatient clinics

No history of recurrent headaches

No chronic medical or psychiatric disorders

Matched with the case group for age and sex

Exclusion Criteria:

• History of neurological disorders other than primary headache
• Previously diagnosed psychiatric conditions
• Autoimmune diseases, chronic infections, severe cardiac failure, metabolic or inflammatory disorders, obesity, or significant hepatic or renal impairment
• Regular use of psychotropic medications or a history of polycythemia
• Use of drugs known to affect uric acid metabolism within 2-4 weeks prior to enrollment
• Cognitive or developmental disabilities limiting the ability to understand or complete study instruments

The study population consists of adolescents aged 12-18 years who present to pediatric neurology outpatient clinics with a confirmed diagnosis of primary headache according to the International Classification of Headache Disorders, 3rd edition (ICHD-3). The control group includes age- and sex-matched adolescents attending general pediatric outpatient clinics who have no history of recurrent headaches or any chronic medical or psychiatric disorders. Participants in both groups must have adequate cognitive ability to understand and complete the study instruments. Exclusion criteria include any neurological disorder other than primary headache, previously diagnosed psychiatric or autoimmune diseases, chronic infections, severe cardiac failure, metabolic or inflammatory disorders, obesity, significant hepatic or renal impairment, regular use of psychotropic medications, history of polycythemia, or use of drugs known to affect uric acid metabolism within 2-4 weeks before enrollment.