Hormones and growth factors involved in supplying offspring: Insights from fish to mammals

A plethora of analogies to support energy provision and offspring nourishment have been posited between mammals and teleosts. This review provides a comprehensive overview of the intricate interactions between hormones and growth factors ranging from early egg development to feeding the newborn in mammals. The discussion encompasses hormones and growth factors in sexual development of male and female bony fish and then focuses on factors relevant during ovarian development and egg and yolk formation in female teleosts. The next chapter focuses on mechanisms to ensure calcium supply for embryo skeletal growth across vertebrate species and the respective maternal calcium mobilisation. Marine and freshwater fish possess divergent strategies for the acquisition of calcium, i.e., mineral homeostasis and osmoregulation. This review will focus primarily on actions of the growth hormone-insulin-like growth factor-system, the parathyroid hormone family, and other signalling factors and hormones. Prolactin is in the literature proposed as an evolutionary link between maternal nutrient supply in mammals, particularly calcium through lactation, and its ancestral role in regulating electrolyte and calcium uptake from the surrounding water in fish. The following section will present some hormones and growth factors in parental care in fish followed by signals in skeletal formation, lactation and calcium homeostasis in soil-egg-laying vertebrates, calcium metabolism in oviparous mammals and during embryonic and postnatal bone formation in placental mammals. Finally, hormones and factors relevant for the development of the mammalian breast are described.