# Androgens and Anabolic Steroids > Androgens and anabolic steroids in MBBS Pharmacology: testosterone preparations and doses, adverse effects, antiandrogens, 5-alpha reductase inhibitors. - Canonical URL: https://prepelephant.com/topics/mbbs/pharmacology/androgens-and-anabolic-steroids - Exam / course: MBBS · Subject: Pharmacology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Androgens and Anabolic Steroids", PrepElephant, https://prepelephant.com/topics/mbbs/pharmacology/androgens-and-anabolic-steroids ## Direct answer Replacement testosterone aims to reproduce physiological levels: injectable enanthate or cypionate 200 mg intramuscularly every two weeks, transdermal gel 5 g (50 mg) daily, or oral testosterone undecanoate 40 mg two to three times daily with a fatty meal (extensive first-pass lymphatic absorption). Aromatisation to oestradiol explains gynaecomastia, and 5-alpha reduction to dihydrotestosterone drives prostate and skin effects — the two pathways organising most adverse reactions: erythrocytosis, HDL-cholesterol fall, acne, lipid worsening, and hypothalamic-pituitary suppression with testicular atrophy and azoospermia. Anabolic steroids — 17-alpha-alkylated derivatives like stanozolol — add hepatotoxicity and are misused for bodybuilding. The therapeutic mirror-image is the antiandrogen group: receptor blockers (flutamide, bicalutamide, enzalutamide), synthesis inhibitors, 5-alpha-reductase inhibitors (finasteride, dutasteride), and steroidogenic antagonists (spironolactone, cyproterone). ## What you must remember - **Preparation logic:** esters lengthen the injection interval (undecanoate in castor oil can go 10-14 weeks); transdermal gel mimics diurnal physiology but risks partner transfer; oral undecanoate needs fat co-ingestion. - **Two activation pathways:** aromatase yields oestradiol (gynaecomastia, bone benefit in men), 5-alpha reductase yields DHT (prostatic growth, androgenetic alopecia) — DHT itself cannot aromatise. - **Dose anchors:** testosterone enanthate 200 mg IM every 2 weeks (or 100 mg weekly for smoother levels); gel 50 mg applied to shoulders; undecanoate 40 mg BD-TDS orally. - **Adverse-effect cascade:** HPG axis suppression (LH/FSH fall, testicular atrophy, infertility), erythrocytosis (check haematocrit), HDL reduction, oedema, sleep apnoea worsening, and stimulation of androgen-dependent carcinoma. - **17-alpha-alkylated steroids:** stanozolol, methyltestosterone — cholestatic jaundice, peliosis hepatis, hepatocellular adenoma; the alkyl group that survives first-pass metabolism is the culprit. - **Antiandrogens by site:** receptor blockers bicalutamide/flutamide (prostate cancer, combined with castration), finasteride 1 mg for alopecia and 5 mg for benign prostatic hyperplasia, spironolactone (receptor blocker plus synthesis inhibitor) for hirsutism, cyproterone for precocious puberty and hypersexuality. - **Flutamide monotherapy paradox:** giving an androgen blocker alone can raise testosterone via LH surge — combine with a GnRH analogue or surgical castration for prostate cancer. - **WADA relevance:** all anabolic steroids are prohibited at all times in sport; testicular atrophy plus a high haematocrit in a gym-going young man is the clinical tell. ## A clinic conversation that carries the whole topic A 55-year-old with fatigue, low libido and morning testosterone of 180 ng/dL (confirmed twice) opts for gel. At review, symptoms have lifted but haematocrit has crossed 54 percent — dose reduction, not discontinuation, is the first move, and venesection if it exceeds 56. His brother, on the other hand, is a 26-year-old bodybuilder using an injectable "cycle" bought in a gym: shrunken testes, tender gynaecomastia and jaundiced sclerae summarise both pathways plus the alkylated oral in his stack; sperm count will take six to twelve months to recover after cessation. Their father, 78, takes finasteride 5 mg for prostatism and asks why his PSA fell by half — 5-alpha-reductase inhibition shrinks the gland and halves PSA independent of cancer, so the threshold for biopsy doubles. Three generations, one receptor family: replacement physiology, abuse toxicology, and therapeutic antagonism. ## Where students slip The classic slip is treating testosterone as the direct androgen at every tissue; in the prostate, skin and hair follicle it is a prohormone, converted by 5-alpha-reductase to the more potent DHT — which is exactly why finasteride shrinks prostates without abolishing libido. Second, candidates forget that DHT and the 5-alpha-reduced androgens cannot aromatise, so pure DHT-like anabolics cause less gynaecomastia but full androgenic skin effects. Third, the infertility point deserves emphasis in the Indian context where parenthood expectations are high: exogenous testosterone suppresses spermatogenesis and is contraindicated in men seeking fertility, for whom the correct drug is human chorionic gonadotropin or clomiphene. ## Frequently asked questions ### Why does testosterone cause gynaecomastia? Peripheral aromatase converts a fraction of the dose to oestradiol, which stimulates breast tissue — dose-related and more obvious with high injectable peaks. ### Which testosterone preparations spare the liver, and which damage it? Esters given intramuscularly and transdermal gels bypass first-pass metabolism and are not hepatotoxic; 17-alpha-alkylated oral steroids cause cholestatic injury and hepatic tumours. ### How does finasteride differ from bicalutamide pharmacologically? Finasteride inhibits 5-alpha-reductase, reducing DHT formation inside the prostate, while bicalutamide blocks the androgen receptor itself and is reserved for prostate cancer therapy. ### Why is exogenous testosterone a poor choice in a man desiring fertility? It suppresses LH and FSH, shutting down intratesticular testosterone and spermatogenesis, producing azoospermia that may take months to reverse. ### What pattern suggests anabolic steroid misuse in a young man? Rapid muscle gain with testicular atrophy, gynaecomastia, severe acne, raised haematocrit and low HDL cholesterol, plus striae and injection-site marks.