Insulin-like 3 (INSL3), a Leydig cell-specific hormone, is essential for testis descent during foetal life and bone metabolism in adults. Insl3-deficient mice exhibit bilateral undescended testes located high in the abdominal cavity. INSL3 is presumed also to conform to a heterodimeric A-B structure of approximately 6 kDa once released from the producing cells. It is possible that both the mature form of INSL3 (6.6 kDa) and the pro-form(s) of INSL3 (12-14 kDa) are secreted from mammalian Leydig cells.
