Nathalie Josso

Nathalie Mühlstein Josso (1934-2022) was a pediatric endocrinologist who studied variations in genital development before birth, including intersex. She was the first to identify anti-Müllerian hormone (AMH), a hormone that plays a major role 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), who was the Polish ambassador to France at the time of their parents' marriage in 1932. The family was Jewish, and as a diplomat, Mühlstein was aware of the dangers his family would face in Nazi-occupied France. He took the family to Lisbon in early June 1940 via Bordeaux, just ahead of France's capitulation. Soon after, the family emigrated to New York. Nathalie was six years old, and she attended school in the US, learning English there. At the end of the war, the Mühlsteins returned to Paris. Her parents had divorced.