Laboratory Tests

Laboratory Tests for Female Patients

For female patients presenting with hair loss, a targeted set of baseline investigations is typically recommended.

Basic Screening

• Hematology: Complete blood count (CBC) – screens for anemia, which is a common reversible cause of hair shedding.
• Iron studies: Ferritin, serum iron, total iron-binding capacity (TIBC). Low ferritin (typically below 40-50 μg/L) is a well-documented contributor to hair loss in women.
• Thyroid function: TSH and free T4 – thyroid dysfunction (both hyper- and hypothyroidism) is a common cause of diffuse hair loss in women.
• Hormonal profile: Testosterone, DHEAS, prolactin – to assess for hyperandrogenism or other endocrine imbalances.
• Nutritional: Vitamin D and zinc – deficiencies are increasingly recognized as contributors to hair shedding.

When to Test Ferritin in Females

Ferritin testing should be considered in the following scenarios:

• Women of childbearing age: Menstrual blood loss is a common cause of iron deficiency.
• Vegetarian or vegan diets: Reduced dietary iron intake may lead to deficiency.
• Pregnancy or postpartum: Increased iron demands during pregnancy and lactation.
• Chronic blood loss: Heavy menstrual bleeding or gastrointestinal bleeding.
• Diffuse hair shedding with no obvious cause: Ferritin should be checked before assuming the cause is genetic.

A ferritin level of at least 40-50 μg/L is generally recommended for optimal hair growth, though some experts suggest 70 μg/L for best results.

Additional Tests for Hirsutism

If the patient presents with hirsutism (excessive male-pattern hair growth) or signs of hyperandrogenism, additional investigations are indicated:

• Total and free testosterone – to assess for androgen excess.
• DHEAS – an adrenal androgen marker.
• 17-hydroxyprogesterone – to screen for late-onset congenital adrenal hyperplasia.
• Pelvic ultrasound – to evaluate for polycystic ovarian morphology, a common finding in polycystic ovary syndrome (PCOS).

Laboratory Tests for Male Patients

For male patients with typical androgenetic alopecia, extensive laboratory testing is not usually indicated as the diagnosis is primarily clinical. However, testing may be considered in specific circumstances.

When to Consider Testing in Males

• Atypical presentation: Sudden, diffuse, or rapidly progressive hair loss.
• Associated symptoms: Fatigue, weight changes, sexual dysfunction, or other systemic signs.
• Poor response to treatment: Lack of expected response to finasteride or minoxidil.
• Suspected thyroid dysfunction: If clinical features suggest hyper- or hypothyroidism.
• Nutritional deficiencies: If dietary history suggests possible deficiency.

When to Consider Testosterone Levels

Testosterone testing in males is generally considered when:

• Hypogonadism is suspected: Symptoms include reduced libido, erectile dysfunction, fatigue, or reduced muscle mass.
• Androgen replacement therapy is being considered: Baseline levels are required before starting treatment.
• Unexplained hair loss with systemic symptoms: To rule out endocrine causes.

For most male patients with typical androgenetic alopecia, routine testosterone testing is unnecessary.

PSA Testing for Patients on Finasteride

Patients over the age of 40 who are considering or currently taking finasteride should undergo baseline PSA (Prostate-Specific Antigen) testing.

Why PSA Testing Is Important

• Finasteride reduces serum PSA levels by approximately 50% in patients taking the medication.
• This reduction is not due to a lower risk of prostate cancer – rather, it is a pharmacological effect that may mask the early detection of prostate conditions.
• To interpret PSA results accurately in patients taking finasteride, the measured value should be multiplied by two to estimate the pre-treatment PSA level.
• This adjustment is necessary to avoid a false sense of security and to ensure that prostate abnormalities are not missed.

When to Test

• Before starting finasteride: A baseline PSA level should be obtained to establish a reference point.
• At 6-12 months after starting: To confirm the expected reduction and establish a new baseline.
• Annually thereafter: As part of routine prostate health monitoring.
• At the discretion of the physician: More frequent testing may be indicated in patients with risk factors or symptoms.

Patients should be counseled that finasteride does not cause prostate cancer, but that PSA monitoring is essential for timely detection of prostate issues.

Liver Function Tests

Routine liver function testing is not required for healthy patients starting finasteride or dutasteride. However, it should be considered in specific situations:

• Patients with known hepatitis: (Hepatitis B or C) – liver function should be monitored regularly as part of overall health management.
• Patients with pre-existing liver disease: Cirrhosis, fatty liver disease, or other hepatic conditions.
• Patients taking other hepatotoxic medications: Concurrent use of medications that may affect liver function.
• Suspected liver dysfunction: Clinical features such as jaundice, dark urine, or elevated baseline liver enzymes.

For patients without liver disease, routine LFT monitoring is not indicated for finasteride or dutasteride therapy alone.

The Role of Vitamin D Testing

Vitamin D plays a role in hair follicle cycling and immune regulation. Testing should be considered when:

• Diffuse hair shedding is present: Vitamin D deficiency is a recognized contributor to telogen effluvium.
• Alopecia areata is diagnosed: Some studies suggest an association with vitamin D deficiency.
• Patients with limited sun exposure: Indoor lifestyles, use of sunscreen, or living in northern latitudes.
• Older adults: Reduced synthesis and dietary intake of vitamin D in the silver hair group.
• Dietary risk factors: Vegetarian or vegan diets may have lower vitamin D intake.

If deficiency is identified, supplementation may be beneficial for general health and potentially for hair growth.

Blood Testing for Oral Minoxidil

Oral minoxidil is used off-label for hair loss at low doses. Before starting treatment, comprehensive blood testing is essential due to potential cardiovascular effects.

Why Testing Is Required

• Risk of pulmonary complications: Oral minoxidil can cause fluid retention, which may lead to pleural effusion (fluid around the lungs) or pericardial effusion (fluid around the heart).
• Cardiovascular effects: Blood pressure and heart rate changes require monitoring.
• Need for baseline data: To establish reference values before starting treatment.
• Compliance with Hong Kong regulations: Oral minoxidil is not registered for use in Hong Kong and should only be prescribed under specialist supervision with appropriate monitoring.

Recommended Testing Protocol

• Baseline (before starting): Complete blood count, renal function, liver function, electrolytes, and a baseline ECG.
• At 2-4 weeks: Repeat blood pressure monitoring and symptom review.
• At 3 months: Repeat blood tests to monitor for changes.
• Every 6-12 months thereafter: Regular monitoring as long as the medication is continued.
• Immediate testing if symptoms develop: Shortness of breath, swelling, palpitations, or unexplained weight gain.

Regular blood tests are not optional – they are a critical safety measure when prescribing oral minoxidil.

Summary: When to Test

• Ferritin (females): Routine screening – aim for ≥40-50 μg/L.
• Ferritin (males): Not routine – consider if anemia suspected.
• PSA (males over 40 on finasteride): Baseline, at 6-12 months, then annually.
• Liver function: Not routine – test if hepatitis, liver disease, or other risk factors present.
• Vitamin D: Consider in diffuse shedding, alopecia areata, older adults, or limited sun exposure.
• Oral minoxidil: Full panel at baseline and regular monitoring – mandatory for safety.