Nathalie Josso

Nathalie Mühlstein Josso (1934–2022) was a pediatric endocrinologist. She studied variations in genital development before birth, including intersex conditions. She was the first to identify anti-Müllerian hormone (AMH), a hormone that is important in the development of male sex in fetuses by suppressing the development of female reproductive organs. Josso also later identified AMH in adult women, enabling the development of tests of ovarian reserve.

Early life and education

Nathalie was born on 13 January 1934 in Paris, the oldest of three children. Her younger sisters are historian Anka Mühlstein (born 1935) and artist Cécile (1936–2007). Their mother Diane (1907–1996) was the daughter of Baron Robert de Rothschild. Their father was Anatol Mühlstein (1889–1957). He was the Polish ambassador to France at the time of their parents' marriage in 1932. Soon after, the family emigrated to New York. Nathalie was six years old, and she attended school in the U.S., learning English there. In addition, when she studied endocrinology her professor was Alfred Jost, who had postulated the existence of a hormone other than testosterone that helped determine male sex after a series of experiments in the 1940s. Although Jost had demonstrated there was a further inhibiting hormone or steroid that was not testosterone, he had not been able to identify it.

Josso gained her PhD in 1971 from the Pierre and Marie Curie University, with a dissertation on Wolffian ducts in fetal rats, under Jost's supervision. Josso also spent some time at the University of Cambridge learning organ culture from Ilse Lasnitzki. She wanted to work on discovering Jost's unidentified substance, and moved to do so at a new INSERM laboratory at the Necker-Enfants Malades Hospital, where she had done her paediatric training. After some struggles with experiments, Josso decided to study calf fetal testes, as these were large. By a series of experiments eliminating other sources, she determined that the substance was being produced in the Sertoli cells.

Josso also maintained some clinical work throughout her scientific career. Intersex conditions also continued to be a focus of her scientific work. In 1981, The Intersex Child was published, an extensive overview of research for paediatricians edited by Josso.

In 1986, Josso's team was one of the first two groups to clone bovine AMH, and the gene of its receptor. The group's results included the development of a blood test for AMH, and identifying the genetic origin of Persistent Müllerian duct syndrome.

Honours

Lawson Wilkins Memorial Lecture, Baltimore (1975) World Federation of Societies for Paediatric Urology Progress Medal (2004)

Personal life

Nathalie and professor of haematology François Josso were married from 1959 until his death from cancer in 1981. The couple had three children, one of whom pre-deceased her mother. Her longtime partner after the death of her husband was Robert Gastone.