Age-related decrease in testosterone levels in men is associated with multiple metabolic, functional and psychosocial consequences. Early identification of modifiable factors associated with decreased testosterone levels may contribute to improved prevention of androgen deficiency and related health conditions.

This population-based analytical cross-sectional observational study aims to investigate anthropometric, functional and lifestyle-related factors associated with decreased total testosterone levels in middle-aged men. Approximately 600 men aged 35-59 years residing in the Andijan region of Uzbekistan will be recruited.

Participants will undergo comprehensive assessment including anthropometric measurements, functional performance tests, standardized questionnaires and laboratory determination of serum total testosterone levels. Anthropometric variables will include body mass index, waist circumference, hip circumference, waist-to-hip ratio and waist-to-height ratio. Functional status will be assessed using hand-grip strength, five-times chair-stand test, 4-meter walk test, balance assessment and the six-minute walk test. Lifestyle-related factors including physical activity, sleep quality, dietary habits, smoking, alcohol consumption and psychoemotional status will be evaluated using validated questionnaires.

The study aims to identify determinants of decreased testosterone levels and develop a predictive model for early identification of androgen deficiency in middle-aged men.

Testosterone plays an important role in maintaining male reproductive health, body composition, muscle strength and metabolic homeostasis. Age-related decrease in testosterone levels has been associated with increased risk of metabolic syndrome, obesity, type 2 diabetes mellitus, cardiovascular diseases, reduced physical performance and impaired quality of life. Despite increasing recognition of androgen deficiency as an important public health issue, many cases remain undiagnosed because of nonspecific clinical manifestations.

Previous studies have demonstrated that obesity, physical inactivity, poor sleep quality, unhealthy dietary patterns and harmful lifestyle habits may influence testosterone levels. However, the complex interactions between anthropometric characteristics, functional status and lifestyle-related determinants remain insufficiently investigated, particularly in population-based studies conducted in middle-aged men.

The present study is designed as a population-based analytical cross-sectional observational study aimed at identifying anthropometric, functional and lifestyle determinants of decreased total testosterone levels in middle-aged men.

Approximately 600 men aged 35-59 years living in the Andijan region of Uzbekistan will be recruited. Participants will undergo anthropometric assessment including height, body weight, body mass index, waist circumference, hip circumference, waist-to-hip ratio and waist-to-height ratio. Functional performance will be evaluated using hand-grip dynamometry, five-times chair-stand test, 4-meter walk test, balance test and six-minute walk test.

Lifestyle-related characteristics will be assessed using standardized questionnaires including the International Physical Activity Questionnaire (IPAQ), Pittsburgh Sleep Quality Index (PSQI), Food Frequency Questionnaire (FFQ), Hospital Anxiety and Depression Scale (HADS), Aging Males' Symptoms Scale (AMS), Androgen Deficiency in Aging Males questionnaire (ADAM) and SARC-F questionnaire. Additional information regarding smoking status, alcohol consumption, occupational characteristics and comorbidities will also be collected.

Venous blood samples will be collected between 7:00 and 10:00 AM following overnight fasting to determine serum total testosterone levels using standardized laboratory methods.

Statistical analysis will include correlation analysis, multivariable logistic regression and receiver operating characteristic (ROC) analysis to identify independent determinants of decreased testosterone levels. Based on the obtained results, a predictive screening model for early identification of androgen deficiency in middle-aged men will be developed.

The results of this study may contribute to improved understanding of modifiable determinants of testosterone deficiency and support development of preventive strategies aimed at improving men's health.

Inclusion Criteria:

• Men aged 35-59 years
• Permanent residence in the Andijan region of Uzbekistan
• Ability to undergo anthropometric measurements and functional performance tests
• Ability to complete study questionnaires
• Provision of written informed consent

Exclusion Criteria:

• Previously diagnosed hypogonadism requiring hormonal therapy
• Current testosterone replacement therapy or other medications affecting androgen status
• Severe cardiovascular, hepatic or renal diseases in the stage of decompensation
• Acute infectious or inflammatory diseases at the time of examination
• Severe psychiatric or cognitive disorders limiting participation
• Clinically significant urological pathology
• Inability or unwillingness to provide informed consent

The study population will consist of middle-aged men aged 35-59 years residing in the Andijan region of Uzbekistan. Participants will be recruited through voluntary participation using community-based announcements, primary healthcare institutions, social media platforms and workplace outreach. Eligible participants will undergo standardized anthropometric assessment, functional performance testing, validated questionnaires evaluating lifestyle-related and psychoemotional factors, and laboratory determination of serum total testosterone levels.