John Walsh holds the positions of Consultant Endocrinologist at Sir Charles Gairdner Hospital in Perth, Western Australia and Clinical Professor in the Medical School at the University of Western Australia. Originally from Scotland, his undergraduate studies were at University College, Oxford and the University of Newcastle upon Tyne in England. He trained in internal medicine in Christchurch, New Zealand, then moved to Australia for advanced training in endocrinology and diabetes in Perth and Melbourne. His doctoral research was in reproductive neuroendocrinology at Prince Henry's Institute of Medical Research (now the Hudson Institute) at Monash Medical Centre, Melbourne.

Since 1999, his primary appointment has been as a clinical endocrinologist at Sir Charles Gairdner Hospital, with an adjunct academic appointment at The University of Western Australia. His clinical interests cover the breadth of endocrinology and diabetes, including pituitary, thyroid and adrenal disease, endocrine neoplasia, calcium disorders and metabolic bone disease. He has two research interests. The first is thyroid disease, encompassing clinical and genetic epidemiology, laboratory diagnosis, clinical management and patterns of care.  The second is calcium pathophysiology and skeletal medicine, including Paget's disease of bone, hyperparathyroidism, and non-canonical effects of vitamin D. He has published over 150 scientific papers.