Trimethylaminuria: the detection of carriers using a trimethylamine load test

J Inherit Metab Dis. 1989;12(1):80-5. doi: 10.1007/BF01805534.


A method potentially of value for investigating putative heterozygotes or carriers of trimethylaminuria by using a single oral dose of trimethylamine (TMA) is described. For healthy volunteers under normal dietary condition and following oral challenge with 300 mg and 600 mg TMA-base, over 90% of the urinary TMA was excreted in the form of TMA (93.6 +/- 1.6%). However, at a dose level of 900 mg TMA-base, there was clear evidence of saturation of the N-oxidation reaction as urinary TMA excretion declined to 77.2% (range 74.8-78.9) of the total dose of TMA. By contrast, in pedigree studies based upon propositi with trimethylaminuria, several parents were identified who showed clear evidence of saturation of the N-oxidation of TMA at the 600 mg TMA-base dose level, but not at 300 mg TMA-base or under normal dietary condition. In these individuals, the proportion of urinary TMA as trimethylamine N-oxide (TMAO) declined to (77.3 +/- 1.7%). Accordingly we propose that the oral administration of 600 mg TMA-base and the analysis of the following 0-8-h urine collection may be useful for the investigation of possible carriers of trimethylaminuria.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Oral
  • Adult
  • Genetic Carrier Screening*
  • Humans
  • Male
  • Metabolism, Inborn Errors / diagnosis
  • Metabolism, Inborn Errors / genetics*
  • Metabolism, Inborn Errors / urine
  • Methylamines / administration & dosage
  • Methylamines / urine*
  • Middle Aged


  • Methylamines
  • trimethyloxamine
  • trimethylamine