RH

From fertilized egg to sexually

mature person

From fertilized egg to sexually mature person

A person grows and develops, from newborn to toddler, child, teenager and then adult. This is not only a development from small to big. Growth means more than attaining a certain height and weight. Growth turns a girl into a woman and a boy into a man; so that these individuals can reproduce. Growth and reproduction are thus very narrowly linked and are dependent on each other. Growth problems in children and young people can influence their future reproductive capabilities. Fertility problems in an adult can be due to damage that occurred before they were born. These correlations have not yet been subject of much scientific investigation and make up the background of the research, patient treatment and educational programs going on at the Department of Growth and Reproduction. The Department treats both children and adults and uses methods from various medical specialities to understand the reasons for problems of growth and reproduction. The goal is of course to develop treatment methods and to find ways to prevent or detect illnesses.

 

Growth (cell division is the fundament of reproduction. Growth and reproductive processes are closely related and are controlled by sexual hormones, growth hormone and growth factors).

 

Lack of knowledge about men

The evolution from fertilized egg to sexually mature male is at the center of the department's activities. The main focus is the development of the adolescent into man and potential father. This choice of priorities has a very practical explanation: andrology, the science of the male body, has been neglected for decades.

New methods of artificial insemination have allowed many childless couples to have a child. This has given us a better understanding of the functioning of the female body. The scientific effort has however been very production-oriented, aimed at generating pregnancies and children. Within this approach the functioning of the male reproductive function has not received much attention. There are big gaps in our knowledge about the male reproductive physiology and at the same time we are facing serious health problems in the area of the male reproductive capacity.

· The incidence of testis cancer has increased by 300 percent in the last 50 years.

· Semen quality has deteriorated during the same period. Research shows that on average there only are half as many sperms cells in the semen as in the beginning of the 1940s.

· Also, during the last 30-50 years, the incidence of genital malformations in newly born boys has doubled. Two of the most frequent malformations are cryptorchidism (a testicle has not descended into the scrotum) and hypospadias (the urethra does not extend to the tip of the penis). Boys with these malformations are at increased risk to develop testis cancer.

We assume that these problems have common roots and that the explanation has to be found in external causes. Harmful influences of the environment may occur during the early months of embryonic development and disturb the delicate mechanisms regulating a boy's growth and sexual development.

At this point we know too little about these delicate mechanisms to be able to understand and explain what is dangerous, when and why. A large part of the research going on at the Department of Growth and Reproduction focuses on obtaining this knowledge.

 

Damage by the environment

It is possible that something goes wrong at the time of fertilization. The fetus may not have the number or the composition of chromosomes characteristic for a normal man or woman. Problems may develop in the first few weeks of the fetus' life, when both genders are extremely vulnerable. It is the time when a girl develops egg cells and when the boy's immature germ cells are developing. They can be damaged for example by radiation or chemicals.

Damage incurred during the embryonic stage can show itself at birth in the form of malformations in the sexual organs. It can show up in later years as growth problems or a premature or delayed puberty. It can appear in an adult's life as cancer of the genitals. Or, it can solely manifest itself as infertility or reduced fertility.

Boys and girls in their childhood and puberty are not very vulnerable to external influences as far as their reproductive capacity is concerned. The girl's eggs are just waiting. The boy's germ cells do not mature either in childhood. If something has gone wrong with the development of the gamete this stays hidden until puberty.

In adults there is a big difference in vulnerability between the male and female gamete. Ovulation causes a dormant egg to become hormonally active. A man is vulnerable from puberty on for the rest of his life. Semen is produced continuously. There is a constant division of cells on the basis of the germ cells that developed in utero. Damaging influences of the environment can thus harm a man's gamete during adulthood. There is a growing recognition that the environment is responsible for the harmful influences, but we do not know how or why.

It is more than likely that many reproductive problems in men have their roots in the embryonic stage. The same is true for most cases of testis cancer and cases of congenital malformation of the sexual organs. It is of the utmost importance to understand the functions of the testicles and the hormonal interaction inside a man's body to avoid damaging influences of the environment  that can harm fertility.

It is of the utmost importance to understand how the development of an embryo's sexual organs takes place and is regulated if we want to be able to prevent damage during that stage.