Soon after, he was admitted to the Royal College of Surgeons in Ireland to finish his medical studies qualifying for practice in 1970. For the next four years he worked for the Medical Research Council laboratory and the department of internal medicine of Jervis Street Hospital. He left this post in 1975 to join the Endocrine oncology research team at the Mater Misericordiae University Hospital as a senior research fellow, and as a leading specialist, he became involved in research into the neurotransmitter substance P. At the same time he completed his doctoral thesis "Inappropriate Production of Hormonal Peptides in Neoplasia".