Thomas John "Jack" Martin is an Australian pathologist, emeritus professor of medicine, physician and academic at University of Melbourne,^[1][3] and researcher who, in 1987, by leading a former team of researchers at the same university, discovered a proteinaceous hormone called parathyroid hormone-related protein (PTHrP).^[4][5] In September 2005, further research was conducted by the team of Dengshun Miao^[6] and David Goltzman at the Calcium Research Laboratory and Department of Medicine, Royal Victoria Hospital of the McGill University Health Centre, and others.^[6]

Martin is a member of Natalie A. Sims' laboratory^[7] at Saint Vincent's Institute of Medical Research.^[8] He works in the institute's Division of Medicine, Dentistry and Health Sciences, and his primary interest is cell biology of bones.^[9]

Martin was the director of St Vincent's Institute from 1988 to 2002.^[10] In September 2005, Martin found that PTHrP produced by osteoblasts is a physiological regulator of bone formation.^[11]

In July 2022, Martin and his team at Natalie A. Sims' lab, after much research on mice, found that deletion of the gene that codes for a receptor protein called granulocyte colony-stimulating factor receptor (G-CSF) increases physiological dysfunction of cortical bones of mice having hyperactivated STAT3 proteins in their bone cells.^[12] Cortical bone maturation depends on SOCS3-mediated suppression of interleukin-6 cytokine-induced STAT3 phosphorylation in bone cells, which form the cellular network embedded in bone matrix. They concluded that G-CSFR signaling could indirectly limit bone resorption and angiogenesis, and thereby has a major role in replacing condensed trabecular bone with lamellar bone during cortical bone formation.^[12]

• In August 2022, an award "TJ Martin Medal" was named in Martin's honour.^[10] The medal was awarded to gastroenterologist Chamara Basnayake at St Vincent's Hospital for his research into the multidisciplinary treatment of functional gastrointestinal disorders.^[10]