Laboratory Tests for Loss of Libido and Perimenopausal Symptoms
For patients presenting with loss of libido and perimenopausal symptoms, morning serum testosterone levels should be checked in addition to follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol, and thyroid function tests.
Primary Laboratory Evaluation
Hormonal Assessment
- Morning serum total testosterone: Essential for evaluating decreased libido in both men and women 1
- Free testosterone levels may be needed if alterations in binding proteins are suspected
- Sex hormone-binding globulin (SHBG) levels should be measured to calculate free androgen index when appropriate
- FSH and LH levels: To determine menopausal status and distinguish between primary and secondary hypogonadism 1
- Estradiol levels: To assess estrogen deficiency contributing to perimenopausal symptoms 1
- Thyroid function tests (TSH, free T4): To rule out thyroid dysfunction that can mimic or exacerbate perimenopausal symptoms 1
Additional Testing Based on Clinical Presentation
- Complete blood count: To rule out anemia which can contribute to fatigue and decreased libido
- Comprehensive metabolic panel: To assess liver function, as liver disease can affect sex hormone metabolism 1
- Prolactin levels: Elevated levels can cause decreased libido and menstrual irregularities
- Fasting glucose/HbA1c: To rule out diabetes which can affect sexual function 1
Interpretation Considerations
For Testosterone Evaluation
- A total testosterone level below the lower limit of normal should be confirmed by repeat testing due to assay variability 1
- Free testosterone assessment using reliable methods (such as equilibrium dialysis) may be needed as standard laboratory assays often have limited reliability 1
- Free androgen index can be calculated as: total testosterone level divided by SHBG level 1
For Menopausal Status Assessment
- FSH > 30 IU/L with low estradiol suggests perimenopause/menopause
- Normal FSH with low testosterone may indicate isolated androgen deficiency 2
- Abnormal LH/FSH ratio may suggest polycystic ovary syndrome or other endocrine disorders
Clinical Pearls and Pitfalls
Important Considerations
- Testosterone levels should be measured in the morning when levels are highest 1
- Single hormone measurements may not reflect tissue-level hormone activity 3
- Low testosterone in regularly menstruating women can cause decreased libido even with normal estrogen levels 2
- Androgen precursor hormones (DHEA-S, Androstenedione) may be normal even when testosterone is low 2
Common Pitfalls
- Failing to consider psychosocial factors that may contribute to decreased libido
- Overlooking medication effects (e.g., antidepressants, beta-blockers) on sexual function
- Relying solely on laboratory values without correlating with clinical symptoms
- Using inappropriate reference ranges for premenopausal vs. perimenopausal women
By systematically evaluating these laboratory parameters, clinicians can better identify hormonal imbalances contributing to loss of libido and perimenopausal symptoms, leading to more targeted treatment approaches.