Hormones and the Fetus

Volume 1: Production, Concentration and Metabolism During Pregnancy

F. A. Kincl,J. R. Pasqualini

• Editore: Pergamon
• Anno: 2013
• ISBN:
  9781483285382
• Argomento: Medicine
• Categoria: Physiology

Written by the world's two leading researchers in steroid biochemistry this volume describes the ways in which hormonal concentration is regulated during pregnancy. It is a comprehensive account of how biosynthesis, metabolism and inter-compartmental transport are related to the concentration of each hormone found in placental, fetal and maternal compartments. There is also an introductory chapter on hormonal mechanism of action.

Chapter 1

Hormonal Mechanisms in Reproduction

Publisher Summary

This chapter examines the unity in hormonal mechanisms in reproduction of different species, while focusing on the functions of the ovary and the uterus, and the hormonal relationships that initiate and maintain reproductive processes. The chain of events that results in fertility depends on balanced interaction of the humoral products of the hypothalamus, gonadotropic hormones secreted by the anterior pituitary gland, and the ovarian steroid hormones. It has been found that many mammals exhibit a characteristic and often disagreeable odor that depends on intact gonadal function. Odors have been implicated not only in the recognition of sexual partners and in sexual arousal but also in the performance of the sexual act and in care of the young. Evidence concerning interdependence between female pheromones and olfactory stimulation and behavioral changes in the male has been documented. Specialized olfactory receptors in most mammals capture these pheromones and stimulate reproductive stimulation. These stimuli initiate the complex cycle of reproductive preparedness in a female subject. The whole cycle of ovulation—the creation and release of the ovarian steroids estrogens and progesterone in the follicle growth of the ovaries, the maturing of the ovaries signaled by the presence of the corpus luteum—is a complex one.

CONTENTS

INTRODUCTION

1 THE HYPOTHALAMO-HYPOPHYSEAL-OVARIAN AXIS

1.1 The Regulatory Function of the Central Nervous System

1.1.1 Olfactory stimulation

1.1.1.1 Female pheromones

1.1.1.2 Male pheromones

1.1.2 Photic stimulation

1.2 The Hypothalamus

1.2.1 Effects on the pituitary gland

1.2.2 Tissue and plasma concentrations of GnRH

1.2.3 Other effects

1.3 The Pituitary

1.3.1 FSH and LH

1.3.1.1 Plasma levels

1.3.2 Prolactin

1.3.2.1 Plasma levels

1.4 Feedback Mechanism

1.4.1 Facilitative action

1.4.1.1 Trigger mechanism

1.4.2 Inhibitory action

1.5 The Hormone Receptors

2 THE OVARY AND THE UTERUS

2.1 Follicle Formation, Ovulation and the Corpus Luteum

2.1.1 Follicle growth

2.1.2 Ovulation

2.1.3 The corpus luteum

2.2 Ovarian Steroidogenesis

2.2.1 Estrogens

2.2.2 Progesterone

2.2.3 Estrogen – progesterone synergism

3 PLASMA GONADAL HORMONE LEVELS DURING THE ESTRUS CYCLE IN DIFFERENT ANIMAL SPECIES

3.1 Patterns of Ovarian Steroids in Plasma and Production Rates During the Human Menstrual Cycle

3.1.1 Pregnenolone and derivatives

3.1.2 Progesterone and derivatives

3.1.3 Estrogens

3.1.3.1 Estradiol, estrone and their sulfates

3.1.3.2 Urinary excretion

3.1.3.3 Estriol

3.1.4 Catechol estrogens

3.1.5 Androgens

3.1.6 Steroids in human endometrial and myometrial tissues

4 PROSTAGLANDINS

4.1 The Luteolytic Effect

5 THE OVIDUCT

5.1 Ova Transport

5.2 Tubal Secretion

6 PREGNANCY

6.1 Implantation

6.2 Gestation

6.2.1 The placenta

6.2.2 Hormonal influences

6.3 Birth and Lactation

REFERENCES

INTRODUCTION

The science of endocrinology is less than a hundred years old. During this brief period, and particularly during the last 40 years, we have come to understand many of the intricate biological mechanisms and hormonal balances that regulate reproductive processes. This understanding has been made possible primarily by advances in molecular biology and the development of experimental techniques and highly sensitive analytical methods. Nevertheless, many aspects still remain obscure.

Most body functions are directed towards a single goal, namely the preservation of the species, and animals have evolved a wide range of biological mechanisms to overcome the problems of perpetuating their kind. Some animals ovulate spontaneously, for example, primates, ungulates and many rodents; in others ovulation is induced, for example the ferret and the rabbit; in other species the reproductive cycle is timed by a biological clock.

Species have evolved differing modes of regulating fertility as adaptations to particular ecological niches. There are some 4000 species of mammals in the world and our knowledge of mammalian reproductive physiology is based on observations from a mere handful. There is a tendency to assume that all mammals conform to some basic reproductive plan. However, there are vast differences between species, and as yet we are only in a position to make generalizations based on the few underlying principles they hold in common.

The endocrine function of the ovary was recognized at the beginning of this century, leading to the search for the active substances. In 1900 Knauer’s classic experiment demonstrated that ovarian transplants could prevent atrophy of the uterus in ovariectomized rabbits. In 1901 and 1903 the German gynecologist L. Fraenkel showed that the corpus luteum was responsible for maintaining pregnancy in rabbits. In 1910 two French biologists, Bouin and Ancel, reported that the corpus luteum brought about a secretory transformation of rabbit endometrium. The search for an estrogenic (“estrus”-inducing) compound in extracts of ovaries, and the pregnancy-maintaining or pro-gestatio (progesterone) substance from corpus luteum, was launched.

Adler, in 1912, prepared a potent, non-identified ovarian extract which exhibited the characteristics of estrogens: administered to immature guinea pigs, it produced estrus and opening of the vagina. The cyclic variations in vaginal smears and cornification of the vaginal epithelium during estrus were first described in 1917 by Stockard and Papanicolaou. In 1923 Allen and Doisy suggested that characteristic changes in the degree of cornification of the lining of the vagina in spayed mice could be used as a biological test for the measurement of estrogenic potency. The assay was easy to reproduce, the reproduction was readily recognized and the results could be evaluated statistically. This procedure was soon being used to quantify the estrogenic potency of biological extracts, and as an index in separation procedures and the preparation of pure estrogenic material. The technique was used to test the estrogenic potency of material from a variety of sources and eventually resulted in the isolation of pure hormones.

The first steroid hormone for which a structure was established was estrone. In 1927 Ascheim and Zondek found that the urine of pregnant women was unusually rich in estrogenic compounds. This became a major source for the isolation and purification of estrone which was isolated in 1929 and 1930 by independent groups, headed by Doisy in the United States and Butenandt in Germany. The determination of its structure was completed 2 years later and was chiefly ...

Indice dei contenuti

• Cover image
• Title page
• Table of Contents
• Inside Front Cover
• Copyright
• Preface
• Chapter 1: Hormonal Mechanisms in Reproduction
• Chapter 2: Biosynthesis and Metabolism of Different Hormones in the Fetal and Placental Compartments
• Chapter 3: Hormone Production and Concentrations During Pregnancy in Humans and in Other Mammalian Species
• Chapter 4: Transfer of Hormones Between the Fetal, Placental and Maternal Compartments
• Chapter 5: Hormonal Changes Preceding Parturition
• Appendix I: The Nomenclature, Structure and Physical Properties of Main Pregnancy Hormones
• Appendix II: Trivial Names and Nomenclature of Steroids Used in This Book
• Index