Factors influencing the effectiveness of administered hormones

Abstract

Endocrine organs concerned in producing chronic effects in the normal body may be supposed to keep up a continuous supply of secretion so that the concentration of the particular hormone in the blood stream neither falls below the required threshold level nor rises sufficiently above it to lead to adverse effects. It has now become clear th at the chief problem in substitution therapy with hormone preparations is so to arrange administration as to imitate the steady continuous activity of the normal glands and avoid alternation of deficiency and wasteful excess of the hormone. Thyroxin alone among the hormones appears to be fairly long-lived in the circulation, so that an excess at a particular time is not necessarily wasteful. On the other hand, the hormones of the gonads, anterior pituitary and adrenal cortex, as well as insulin, seem to be used, excreted or destroyed soon after entering the circulation. Quantitative and sometimes even qualitative results with these hormones have depended on the method of administration adopted in assay work. In the case of oestrogenic preparations, from ovary or urine, attention was early directed to the variation in apparent activity due to the method of administration. The significant facts in this connexion have been recently reviewed (Parkes 1937). A constant total dose of oestrone, oestradiol or ovarian extract in either oily or aqueous solution, is much more effective if given as a series of small doses than if given as a single dose. The effect of divided dosage can be simulated by appropriate esterification of the hormone.