Norboletone (INN) (former proposed brand name Genabol), or norbolethone, is a synthetic and orally active anabolic–androgenic steroid (AAS) which was never marketed.[1] It was first developed in 1966 by Wyeth Laboratories and was investigated for use as an agent to encourage weight gain and for the treatment of short stature, but was never marketed commercially because of fears that it might be toxic.[1][2] It subsequently showed up in urine tests on athletes in competition in the early 2000s.[3]

Clinical data
Other namesNorbolethone; 17α-Ethyl-18-methyl-19-nortestosterone; 17α-Ethyl-18-methylestr-4-en-17β-ol-3-one; 13β-Ethyl-17α-hydroxy-18,19-dinorpregn-4-en-3-one
Routes of
By mouth
Drug classAndrogen; Anabolic steroid
ATC code
  • None
Legal status
Legal status
CAS Number
PubChem CID
CompTox Dashboard (EPA)
Chemical and physical data
Molar mass316.485 g·mol−1
3D model (JSmol)

Norboletone was found to have been brought to the market by the chemist Patrick Arnold, of the Bay Area Laboratory Co-operative (BALCO), an American nutritional supplement company. It is reputed to have been the active ingredient in the original formulation of the "undetectable" steroid formulation known as "The Clear" before being replaced by the more potent drug tetrahydrogestrinone.[4][5]

In 2002, Don Catlin, the founder and then-director of the UCLA Olympic Analytical Lab, identified norboletone for the first time in an athlete's urine sample. In the same year, U.S. bicycle racer Tammy Thomas was caught using it and was banned from her sport.[2] The following year, Catlin identified and developed a test for tetrahydrogestrinone (THG), the second reported designer anabolic sample—a key development in the BALCO Affair.[6]

Norboletone is on the World Anti-Doping Agency's list of prohibited substances,[7] and is therefore banned from use in most major sports.


  1. ^ a b Mark Fainaru-Wada; Lance Williams (23 March 2006). Game of Shadows: Barry Bonds, BALCO, and the Steroids Scandal that Rocked Professional Sports. Penguin Publishing Group. pp. 75–. ISBN 978-1-101-21676-7.
  2. ^ a b Lee, Henry K. (2006-08-04). "Inventor of 'clear' steroid gets 3 months in prison". The San Francisco Chronicle.
  3. ^ Catlin DH, Ahrens BD, Kucherova Y (2002). "Detection of norbolethone, an anabolic steroid never marketed, in athletes' urine". Rapid Communications in Mass Spectrometry. 16 (13): 1273–1275. doi:10.1002/rcm.722. PMID 12112254.
  4. ^ "Chemist Who Created "The Clear" Sentenced" (Press release). United States Attorney for the Northern District of California. 2006-08-04. Archived from the original on 2006-10-14. Retrieved 2007-10-08.
  5. ^ Knight J. (2003). "Drugs bust reveals athletes' secret steroid". Nature. 425 (6960): 752. doi:10.1038/425752a. PMID 14574369.
  6. ^ "Catlin has made a career out of busting juicers". USA Today. 2007-02-28.
  7. ^ "The World Anti-Doping Code: The 2012 Prohibited List" (PDF). World Anti-Doping Agency. Archived from the original (PDF) on 2012-05-13. Retrieved 2012-07-17.