Troy was born to Joseph Troy a hatter and outfitter, and his wife Hanna ('Johanna') (née Doran) in Ranelagh on 14 September 1914. She had two sisters and two brothers. She attended school at
Loreto College, St Stephen's Green. Initially her mother persuaded her not to study medicine so she studied pharmacy in
University College Dublin and graduated first in her class c.1936. Later she went back and studied medicine gaining her MB, B.Ch. and BAO with honours from UCD in 1940). She completed her internship in both
St. Vincent's University Hospital and the
Coombe Women & Infants University Hospital, and stayed with them for her postgraduate training. She also trained with
Temple Street Children's University Hospital. ==Career==