This cross-sectional observational study aims to evaluate the relationship between serum prolactin levels, peripheral inflammatory markers (NLR, PLR, SII, CRP), and disease severity in patients with Parkinson's disease (PD). A total of at least 300 patients diagnosed with idiopathic PD will be included. Disease severity will be assessed using the Unified Parkinson's Disease Rating Scale (UPDRS) and the Modified Hoehn-Yahr staging system. Serum and salivary prolactin levels will be measured using ELISA, while inflammatory markers will be calculated from routine blood tests. The study seeks to clarify whether prolactin and systemic inflammation indicators may serve as non-invasive biomarkers for disease progression and prognosis in PD, with particular emphasis on postmenopausal women.

Inclusion Criteria:

• Age ≥ 18 years
• Diagnosis of idiopathic Parkinson's disease confirmed by a neurologist
• Both male and postmenopausal female patients
• Patients able to provide informed consent
• Clinically stable enough to undergo blood and saliva sampling, as well as neurological assessment

Exclusion Criteria:

• Premenopausal female patients
• Patients with secondary or atypical parkinsonism (e.g., drug-induced, vascular, atypical parkinsonian syndromes)
• Known endocrine disorders affecting prolactin levels (e.g., prolactinoma, pituitary adenoma, hypothyroidism)
• Use of medications known to alter prolactin secretion (e.g., antipsychotics, dopamine antagonists, estrogen therapy)
• History of other neurodegenerative diseases (e.g., Alzheimer's, Huntington's)
• Presence of active infection, chronic inflammatory disease, or malignancy
• Severe renal, hepatic, or cardiac failure
• Inability to provide informed consent

The study population will consist of at least 300 adult patients (≥18 years) diagnosed with idiopathic Parkinson's disease who are followed at the Neurology Department of Çanakkale Onsekiz Mart University. Both male and postmenopausal female patients will be included. Participants must be clinically stable and able to undergo neurological evaluation, serum and salivary prolactin testing, and routine laboratory investigations. Patients with atypical or secondary parkinsonism, endocrine disorders affecting prolactin levels, active infection, chronic inflammatory disease, or malignancy will be excluded.