There are multiple definitions:

1. hormone replacement therapy(English)

   • ERT, TRT
   • Hormone, Therapeutic approaches
   • https://doi.org…srev.00041.2022

2. heart rate turbulence(English)

   • CVHR, HRV, HR
   • Electrophysiology, Cardiology, Variability / oscillation

3. Habit and Reversal Training(English)

   • e.g. for treating trichotillomania, which is an impulse control disorder characterized by intense and repeated urge to pull out hairs with a mounting tension before and a sense of relief afterwards
   • TTM
   • Behavior(al science), Psychology, Therapeutic approaches
   • https://doi.org…0974-7753.96089

4. human respiratory tract [system](English)

   • ACI, AIM, AIM-pHRT, CPM, EPM, FPM, OIP, pHRT, QC, USP
   • Respiratory system, Pharmacology / pharmaceutics
   • https://doi.org…/jamp.2011.0925

5. Heidelberg Retina Tomograph(English)

   • refers to corneal modifications induced by either femtosecond laser or mechanical microkeratome
   • LASIK
   • Ophthalmology
   • https://doi.org…67/iovs.05-1207