Hi!
See e.g., SDTM IG v3.1.2 on page 35:
"4.1.3.2 CONTROLLED TERMINOLOGY TEXT CASE
It is recommended that controlled terminology be submitted in upper case text for all cases other than those
described as exceptions below. Deviations to this rule should be described in the define.xml.
a. If the external reference for the controlled terminology is not in upper case then the data should
conform to the case prescribed in the external reference (e.g., MedDRA and LOINC).
b. Units, which are considered symbols rather than abbreviated text (e.g., mg/dL). "
Regards,
Sergiy