Growth as affected by general hormonal factors and hormonal balances, and the limitations of such studies.

Many elements are implicated in fetal and postnatal growth ; the hormonal factors are discussed in this review. In the first section, general hormonal effects on the growth of domestic animals are reviewed with special emphasis on the role of the pituitary and its hormones (growth hormone, prolactin, ACTH) ; somatomedin action is considered in this perspective. The effects of the thyroid and its hormones, the adrenal cortex and corticosteroids, gonads and sex steroids and insulin are discussed. In the second part of this review, the problem of hormonal balance and growth during fetal and postnatal life is analyzed. The complementarity of the « growth activities » of the growth hormone (GH) and the placental somatotropic or lactogenic hormone (CS or PL) during fetal life is emphasized. The relations between these hormones, somatomedins and fetal development are reviewed in detail : thyroid hormones and estrogens as well as insulin may also play a role in fetal development. In neonatal life the correlations between plasma hormone concentrations and growth are more or less strict. These levels depend on the kinetic factors of hormone metabolism whose correlation to growth has been studied. The mode ot action of some hormonal treatments and the effect of selection on some hormonal balances are also discussed. In the third part of this report, a critical study indicates the limitations in investigations