When to Stop

• Endometrial cancer / endometrial hyperplasia (women only) — ~2-3× increased risk over baseline in postmenopausal women on chronic tamoxifen. Boxed warning. Irrelevant in men.
• Venous thromboembolism (VTE) / DVT / PE — ~2-3× over baseline; lower than raloxifene's relative risk per STAR. Highest risk in first 12 months. Risk factors: prior VTE, immobilization, surgery, malignancy, smoking, obesity. Discontinue 72+ hours pre-surgery.
• Stroke — small but elevated incidence, particularly in postmenopausal women with CV risk factors.
• Cataracts — long-term (years) tamoxifen elevates cataract incidence. STAR trial showed higher cataract rate vs. raloxifene.
• Retinal toxicity / retinopathy — rare but documented; "tamoxifen retinopathy" includes crystalline deposits, macular edema. Stop immediately on visual changes.
• Hepatotoxicity — rare; case reports of severe hepatic dysfunction including fatal outcomes. Routine LFT monitoring not mandated but check baseline.
• Severe hypersensitivity — rare (Stevens-Johnson syndrome reports exist but extremely rare).
• Hypercalcemia — in patients with bone metastases (paradoxical bone-resorption effect during tumor flare).
• Tumor flare — early breast cancer treatment can produce paradoxical pain/symptom worsening before regression.
• First 4 weeks: Hot flushes, mood changes, headache most common — usually fade.
• First 12 months: Highest VTE risk window.
• Any visual change at any time: Stop immediately, ophthalmology referral, do not rechallenge.
• Year 1+ on chronic use: Cataract surveillance via routine eye exam.
• Pre-surgery: Discontinue ≥72 hours pre-elective procedure.
• CYP2D6-PM genotype on the user's 23andMe (~June 2026): Would predict reduced endoxifen formation if ever indicated — though for short-term male PCT use, the implications are smaller than for long-term breast cancer therapy.
• MMA training = repeated soft tissue trauma + impact: trauma is a VTE risk factor; tamoxifen compounds that risk. Less concerning than raloxifene (lower VTE multiplier per STAR) but real.
• Daily light training + ground game: prolonged static positioning + acute injury creates VTE windows.
• 6-12hr cognitive computer work + visual demand: any drug with non-trivial visual side-effect rate is a non-starter for someone whose primary asset is brain output requiring sustained visual attention.
• V5 bupropion option: moderate CYP2D6 inhibitor — would impair tamoxifen → endoxifen conversion if ever co-prescribed. Not a current concern but flag for future.
• Eugonadal HPG axis at peak: tamoxifen's hypothalamic partial antagonism would modestly elevate already-peak LH/FSH/T — unpredictable in a system at peak; no demonstrated benefit.
• Net: zero indication, real risk surface, libido/mood/vision downside — unfavorable on every axis at his current profile.