Testosterone chemical structure (androgen steroid), 2D skeletal formula, C19H28O2, CAS 58-22-0

Testosterone Chemical Structure

by

1. Identification

Summary

Testosterone is an endogenous androgen used therapeutically for male hypogonadism (primary or hypogonadotropic) and certain other indications. It acts via androgen receptor (AR) agonism and through metabolites dihydrotestosterone (5-α-reduction) and estradiol (aromatization).

Brand Names

Multiple by formulation (e.g., transdermal gels/patches, IM esters, pellets; region-dependent)

Name

Testosterone

Background

Principal male sex hormone; administered as base (transdermal, buccal, nasal) or as long-acting esters (e.g., cypionate, enanthate, undecanoate) for depot delivery.

Modality

Small molecule

Groups

Approved; prescription/controlled (jurisdiction-specific)

Structure

Testosterone 2D chemical structure (C19 androstane; 3-keto, 17β-hydroxy). Formula C19H28O2; IUPAC 17β-hydroxyandrost-4-en-3-one; CAS 58-22-0.
Testosterone chemical structure (androgen steroid), 2D skeletal formula, C19H28O2, CAS 58-22-0

Weight

~288.42 g/mol (free base)

Chemical Formula

C₁₉H₂₈O₂

Synonyms

17β-hydroxyandrost-4-en-3-one; Androst-4-en-17β-ol-3-one

External IDs

CAS: 58-22-0; PubChem CID: 6013; UNII: 3XMK78S47O; ATC: G03BA03

2. Pharmacology

Indication

Male hypogonadism (primary or hypogonadotropic); delayed puberty in males (selected cases); palliative use in some inoperable breast cancers (product-/region-specific).

Associated Conditions

Hypogonadism symptoms/signs (low serum T confirmed), osteoporosis/low bone mass related to androgen deficiency; gender-affirming hormone therapy (clinical practice, off-label in some regions).

Associated Therapies

IM depot esters (cypionate, enanthate, undecanoate), transdermal gel/patch, nasal and buccal formulations, subcutaneous pellets.

Contraindications & Blackbox Warnings

Contraindicated in men with breast or known/suspected prostate cancer, women who are or may become pregnant, and in hypersensitivity to components.
Major warnings by product: erythrocytosis/polycythemia, worsening BPH/urinary symptoms, potential blood pressure increase (some formulations), lipid changes, edema, sleep apnea, thromboembolic events; pulmonary oil microembolism/anaphylaxis warning with certain undecanoate IM products (REMS in some markets).

Pharmacodynamics

Binds AR → gene transcription driving virilization, anabolism, and erythropoiesis; peripheral conversion to DHT (potent AR agonist) and estradiol (bone/brain effects).

Mechanism of action

AR agonism; 5-α-reductase → DHT; aromatase → estradiol; broad tissue-specific actions via receptor distribution/co-regulators.

Absorption

Route-dependent:
• Transdermal: systemic absorption from gel/patch; steady state in days.
• IM esters: slow release from oil depot.
• Oral undecanoate: lymphatic uptake; fat-dependent absorption.
• Oral base: poor (extensive first-pass metabolism).

Volume of distribution

Large, with extensive tissue distribution (steroid class).

Protein binding

High (~98%): to SHBG and albumin; ~1–2% free fraction.

Metabolism

Hepatic: 5-α-reduction (→ DHT), aromatization (→ estradiol), and phase II conjugation (e.g., UGT2B17 glucuronidation) to inactive metabolites.

Route of elimination

Primarily urine (~90%) as glucuronide/sulfate conjugates; feces ~6% (metabolites).

Half-life

Free testosterone in plasma: variable, ~10–100 min (short).
Depot esters (e.g., cypionate): apparent t½ ~8 days IM; others formulation-dependent.

Clearance

Predominantly hepatic metabolic clearance; conjugate renal excretion.

Adverse Effects

Acne, seborrhea, alopecia (androgenic), gynecomastia (aromatization), mood/libido changes, erythrocytosis (↑Hct), edema, hypertension (some products), fertility suppression (↓spermatogenesis), injection/dermal site reactions; rare serious thromboembolic and cardiovascular events (risk signals product-/population-dependent).

Toxicity

Overexposure/abuse (anabolic-androgenic steroid misuse): hepatic strain (notably with 17-α-alkylated agents, less with testosterone), psychiatric effects, dyslipidemia, endocrine suppression. Supportive management; taper under medical care.

Pathways

AR signaling; 5-α-reduction and aromatase pathways; conjugation and urinary excretion of 17-ketosteroid derivatives.

Pharmacogenomic Effects/ADRs

UGT2B17 deletion polymorphism affects urinary excretion profiles (forensic/analytical relevance). SRD5A2 variants modulate DHT formation; AR CAG repeat length influences sensitivity (research/clinical nuance).

3. Interactions

Drug Interactions

Oral anticoagulants (e.g., warfarin): potentiation (↑INR) reported; monitor.
Insulin/antidiabetics: dose adjustments may be needed.
Corticosteroids: additive edema/fluid retention.
Drugs altering SHBG (e.g., thyroxine) can shift free T fraction.

Food Interactions

Oral undecanoate: high-fat meal increases absorption; follow product labeling.

4. Categories

ATC Codes

G03BA03 (androgens)

Drug Categories

Androgen; Anabolic steroid; Endogenous hormone; Small molecule

Chemical Taxonomy

C19 androstane steroid with 3-keto and 17β-hydroxy groups; Δ⁴-ene.

Affected organisms

Humans (therapeutic use)

5. Chemical Identifiers

UNII

3XMK78S47O

CAS number

58-22-0

InChI Key

MUMGGOZAMZWBJJ-DYKIIFRCSA-N

InChI

InChI=1S/C19H28O2/c1-18-9-7-13(20)11-12(18)3-4-14-15-5-6-17(21)19(15,2)10-8-16(14)18/h11,14-17,21H,3-10H2,1-2H3/t14-,15-,16-,17-,18-,19-/m0/s1

IUPAC Name

(8R,9S,10R,13S,14S,17S)-17-hydroxy-10,13-dimethyl-1,2,6,7,8,9,11,12,14,15,16,17-dodecahydrocyclopentaaaaphenanthren-3-one
(Short: 17β-hydroxyandrost-4-en-3-one)

SMILES

O=C1C=C2C@(CC1)[C@H]3CC[C@]4(C)C@HO

6. References

PubChem record for Testosterone (CID 6013) — identifiers, formula, synonyms. PubChem
CAS Common Chemistry — CAS 58-22-0, InChI, InChIKey MUMGGOZAMZWBJJ-DYKIIFRCSA-N, canonical SMILES. commonchemistry.cas.org
precisionFDA/UNII — UNII 3XMK78S47O (Testosterone). precisionFDA
WHOCC ATC/DDD Index — G03BA03 classification. ATCDDD
DailyMed (testosterone cypionate) — IM depot t½ ~8 days, ~90% urine conjugates / ~6% feces, hepatic inactivation. DailyMed+1
DailyMed (testosterone gel) — plasma half-life range ~10–100 min for free testosterone reported. DailyMed

Leave a Comment