The Unified Medical Language System® (UMLS®) Metathesaurus (MTH) was developed and is maintained by the U.S. National Library of Medicine (NLM).
MTH is used by the NLM in the construction of the UMLS Metathesaurus.
MTH contains concept names, attributes, relationships, and other data that were created by NLM to facilitate construction of the UMLS Metathesaurus.
Metathesaurus Update Frequency
MTH is an updated source in each Metathesaurus release.