The type-1 insulin-like growth-factor receptor (IGF-1R) and insulin re
ceptor (IR) are closely related members of the tyrosine-kinase recepto
r superfamily(1). IR is essential for glucose homeostasis(2), whereas
IGF-1R is involved in both normal growth and development and malignant
transformation(3). Homologues of these receptors are found in animals
as simple as cnidarians(4).