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Systematic (IUPAC) name
Clinical data
AHFS/Drugs.com Consumer Drug Information
  • US: C (Risk not ruled out)
Routes of
Pharmacokinetic data
Protein binding ~85%
Metabolism Hepatic
Excretion Renal
CAS Number 968-93-4 YesY
ATC code none
PubChem CID 13769
DrugBank DB00894 YesY
ChemSpider 13172 N
KEGG D00153 YesY
Chemical data
Formula C19H24O3
Molar mass 300.39 g/mol
 NYesY (what is this?)  (verify)

Testolactone (brand name Teslac) is an antineoplastic agent that is a derivative of progesterone and is used to treat advanced stage breast cancer.[1]

It is nonselective.[2]


Testolactone is a synthetic antineoplastic agent that is structurally distinct from the androgen steroid nucleus in possessing a six-membered lactone ring in place of the usual five-membered carbocyclic D-ring. Despite some similarity to testosterone, testolactone has no in vivo androgenic effect. No other hormonal effects have been reported in clinical studies in patients receiving testolactone.[3]

Mechanism of action[edit]

The principal action of testolactone is reported to be inhibition of steroid aromatase activity and the reduction in estrone synthesis that follows. Androstenedione, a 19-carbon steroid hormone produced in the adrenal glands and the gonads, is where estrone synthesis originates and is the source of estrogen in postmenopausal women. In vitro studies report that the aromatase inhibition may be noncompetitive and irreversible, and could possibly account for the persistence of this drug's effect on estrogen synthesis after drug withdrawal.[3]


This drug is mainly used for treating various types of breast cancer in women who have been through menopause or whose ovaries no longer function.[4] It works by blocking the production of estrogen, which helps prevent the growth of breast cancers that are activated by estrogen. It may also prevent tumor cells from being activated by other hormones.[4] It also has been used to postpone precocious puberty because of its ability to block estrogen production.[5]

Side effects[edit]

The most common side effects include:

  • Abnormal skin sensations
  • Aches of the legs and arms
  • General body discomfort
  • Hair loss
  • Loss of appetite
  • Nausea
  • Redness of the tongue
  • Vomiting


  1. ^ Testolactone at DrugBank.ca
  2. ^ Dunkel L (July 2006). "Use of aromatase inhibitors to increase final height". Mol. Cell. Endocrinol. 254-255: 207–16. doi:10.1016/j.mce.2006.04.031. PMID 16766117. 
  3. ^ a b DrugBank: DB00894 (Testolactone)
  4. ^ a b Testolactone facts and comparisons at Drugs.com
  5. ^ Carel, J.-C.; Lahlou, N; Roger, M; Chaussain, JL (2004). "Precocious puberty and statural growth". Human Reproduction Update 10 (2): 135–47. doi:10.1093/humupd/dmh012. PMID 15073143.