This study aims to investigate the relationship between the atherogenic index of plasma (AIP) and the therapeutic response to daily tadalafil 5 mg treatment in patients diagnosed with vascular erectile dysfunction (VED). AIP is considered a marker of atherogenic dyslipidemia and subclinical atherosclerosis and is calculated using the formula log10 (triglycerides/HDL-C). Since vascular abnormalities play a major role in the pathophysiology of erectile dysfunction, AIP may reflect underlying vascular risk and potentially predict treatment outcomes. In this prospective observational study, patients with vascular erectile dysfunction will receive tadalafil 5 mg once daily for one month, and treatment response will be evaluated by comparing clinical parameters before and after therapy.

The Atherogenic Index of Plasma (AIP) has been widely accepted as an indicator of atherogenic dyslipidemia and subclinical atherosclerosis. It is a simple laboratory-based parameter calculated using the formula log10 (triglycerides/HDL-C) and has been associated with increased cardiovascular risk. Vascular erectile dysfunction (VED) represents one of the most important organic causes of erectile dysfunction and results from vascular abnormalities that impair adequate penile blood flow.

Tadalafil 5 mg administered once daily is an established treatment option for patients with vascular erectile dysfunction. However, the variability in treatment response suggests that underlying vascular risk factors may influence therapeutic outcomes. Identifying predictive biomarkers that can estimate treatment response may improve patient selection and treatment strategies.

The primary objective of this study is to evaluate whether AIP levels are associated with the response to tadalafil treatment in patients with vascular erectile dysfunction. The study also aims to assess the relationship between lipid profile parameters and the severity of erectile dysfunction, as well as to identify potential predictors of treatment response.

This study is designed as a prospective observational study. Participants diagnosed with vascular erectile dysfunction will receive tadalafil 5 mg once daily for a period of one month. Clinical and laboratory evaluations will be performed before and after treatment. The findings of this study are expected to determine whether AIP can serve as a potential biomarker for predicting the therapeutic response to tadalafil in patients with vascular erectile dysfunction.

Inclusion Criteria:Men older than 40 years of age who have been diagnosed with vascular erectile dysfunction, have had symptoms for at least three months, have been considered suitable for tadalafil treatment, and have received tadalafil therapy for at least four weeks.

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Exclusion Criteria:Use of nitrates

Uncontrolled cardiac arrhythmias

Hypotension

Diagnosis of hypogonadism

History of major cardiovascular events within the last 6 months (including uncontrolled hypertension or severe ischemic heart disease)

Severe hepatic or renal insufficiency

Patients receiving hormone replacement therapy

Patients diagnosed with psychogenic, neurological, hormonal, or pharmacological erectile dysfunction

History of radical pelvic surgery

Anatomical abnormalities of the penis

History of non-arteritic anterior ischemic optic neuropathy (NAION)

Retinitis pigmentosa

Known hypersensitivity to tadalafil or other phosphodiesterase type-5 inhibitors

Alcohol or substance abuse

Use of other treatments for erectile dysfunction

Unstable diabetes mellitus

History of medications affecting lipid profile (such as corticosteroids or certain antidepressants)

Initiation or dose modification of lipid-lowering therapy (e.g., statins, fibrates) within the last 3 months

Uncontrolled thyroid dysfunction

Active infection or inflammatory conditions

Patients receiving active cancer treatment

Inability to comply with study procedures

Beck Depression Inventory score greater than 0

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The study population will consist of men older than 40 years who have been diagnosed with vascular erectile dysfunction and are considered suitable candidates for tadalafil therapy. Participants must have experienced symptoms of erectile dysfunction for at least three months. Eligible patients will receive tadalafil 5 mg once daily for a period of at least four weeks. Patients with significant comorbid conditions, contraindications to tadalafil therapy, or other causes of erectile dysfunction will be excluded according to the predefined exclusion criteria.

Individual participant data will not be shared to protect participant confidentiality and because the study was not designed with a data-sharing plan.