NSABP P-1: Tamoxifen for Breast Cancer Prevention
Journal of the National Cancer Institute (1998)
Reduced invasive breast cancer incidence by 49% in high-risk women, first chemoprevention agent for breast cancer.
Tamoxifen
Oral tablet (20mg)Available in all 50 statesMarketing purposes only. Actual medications, if prescribed, are dispensed by a licensed pharmacy.
hormones
TamoxifenTamoxifen
First-generation SERM, cornerstone treatment for HR+ breast cancer. In men, used for gynecomastia and as fertility-preserving adjunct to TRT by stimulating LH/FSH through hypothalamic estrogen receptor antagonism.
Reduces breast cancer recurrence by 40 to 50%
Raises testosterone in men via hypothalamic SERM effect
Preserves spermatogenesis
Preserves bone in premenopausal women
No commitment · HSA/FSA eligibleNo commitment · HSA/FSA eligible
How it works
Mechanism of action
Active metabolite endoxifen (via CYP2D6) competes at estrogen receptors. Antagonist in breast; partial agonist in bone, endometrium, and liver. Blocks negative estrogen feedback in hypothalamus, increasing GnRH, LH, FSH, and testosterone in men.
The baseline panel.
Every Marek client receives this baseline panel before a provider review. Your provider may add additional biomarkers based on your health history, symptoms, and goals, pulling from 1,000+ available markers. See more biomarkers →
Hormone Profile
12 markers
Sex hormones
- Total TestosteroneLC/MS
- Free TestosteroneEquilibrium Dialysis
- Estradiol, Sensitive / UltrasensitiveLC/MS
- Sex Hormone Binding Globulin (SHBG)
- ProgesteroneLC/MSFemale panel
- Prolactin
- Luteinizing Hormone (LH)
- Follicle-Stimulating Hormone (FSH)
- hCG, Total, QuantitativeFemale panel, pre-menopause
Adrenals & neurosteroids
- Cortisol
- DHEA-S
Growth hormone / IGF-1
- Insulin-Like Growth Factor I (IGF-1)
Thyroid Status
3 markers
Thyroid hormones
- Thyroid Stimulating Hormone (TSH)
- Free T4
- Free T3
Heart Health
9 markers
Cardiovascular health
- Total Cholesterol
- HDL Cholesterol
- LDL Cholesterol
- LDL:HDL Ratio
- VLDL Cholesterol
- Triglycerides
- Apolipoprotein-B (ApoB)
- C-Reactive Protein, High Sensitivity (hsCRP)
- Lipoprotein(a) (Lp(a))
Metabolism
3 markers
Insulin sensitivity
- Blood Glucose
- Fasting Insulin
- HbA1c
Organ Function
26 markers
Liver & pancreas
- AST
- ALT
- Bilirubin, Total
- γ-Glutamyl Transferase (GGT)
Kidney function
- BUN
- Creatinine w/ eGFR
Comprehensive Metabolic Panel (CMP)
- Glucose
- Blood Urea Nitrogen (BUN)
- Creatinine
- eGFR
- BUN/Creatinine Ratio
- Sodium
- Potassium
- Chloride
- Carbon Dioxide, Total
- Calcium
- Protein, Total
- Albumin
- Globulin, Total
- Albumin/Globulin (A/G) Ratio
- Alkaline Phosphatase (ALP)
- AST
- ALT
Prostate health
- Prostate-Specific Antigen (PSA)Male panel
- Free PSAMale panel
- % Free PSAMale panel
Nutrient Status
31 markers
Vitamins & minerals
- Vitamin D, 25-OHD (25-Hydroxy)
- Magnesium, RBC
Iron status
- Iron
- Iron Saturation
- TIBC
- UIBC
- Ferritin
Complete Blood Count (CBC)
- White Blood Count (WBC)
- Red Blood Count (RBC)
- Hemoglobin (Hgb)
- Hematocrit (HCT)
- MCV
- MCH
- MCHC
- Red Cell Distribution Width (RDW)
- Platelets
- Neutrophils
- Neutrophils (Absolute)
- Lymphocytes
- Lymphocytes (Absolute)
- Neutrophil/Lymphocyte Ratio
- Monocytes
- Monocytes (Absolute)
- Eosinophils
- Eosinophils (Absolute)
- Basophils
- Basophils (Absolute)
- Immature Cells
- Immature Granulocytes
- Immature Granulocytes (Absolute)
- NRBC, w/ Reflex for Immature Cells
Clinical evidence
The research behind Tamoxifen.
Safety profile
Monitoring & safety information.
Commonly reported side effects
- Hot flashes
- Vaginal dryness
- Mood changes
- Weight gain
Less common but serious risks
- Endometrial cancer (2 to 3x risk in women)
- VTE (2 to 3x risk)
- Stroke
- Drug interaction with CYP2D6 inhibitors (SSRIs)
Generally not appropriate for
- History of VTE (relative)
- Pregnancy
- Concurrent strong CYP2D6 inhibitors
Typical monitoring
- Annual gynecological exam (women)
- Ophthalmologic exam (long-term)
- Lipid panel
- Liver function
- Testosterone, LH/FSH, estradiol (men)
FAQ
Quick answers.
First-generation SERM, cornerstone treatment for HR+ breast cancer. In men, used for gynecomastia and as fertility-preserving adjunct to TRT by stimulating LH/FSH through hypothalamic estrogen receptor antagonism.
Reduces breast cancer recurrence by 40 to 50%. Raises testosterone in men via hypothalamic SERM effect. Preserves spermatogenesis. Preserves bone in premenopausal women.
Common side effects include: hot flashes, vaginal dryness, mood changes, weight gain. Most side effects are dose-dependent and may resolve with continued use or dose adjustment.
First-generation SERM, cornerstone treatment for HR+ breast cancer. In men, used for gynecomastia and as fertility-preserving adjunct to TRT by stimulating LH/FSH through hypothalamic estrogen receptor antagonism.
Treatments are dependent on licensed clinical prescription. Client costs vary based on individual labs and panel in treatments and services.