The study of prenatal development provides many clues for understanding
the physiology as well as the pathogeny of malformations and many
diseases. I became interested in the analysis of human development as a
young medical student more than 30 years ago, and I have stayed in this
field all my life. In my studies, I always tried to compare the events
of different disciplines such as genetics, anatomy, bio- chemistry and
physiology. I learned that the development of a structure is, under
normal circumstances, strictly determined and that the development of
structures always precedes their proper function. There are no changes
in function without changes in structure. The life of every cell is
genetically preprogrammed and the program may be modified by complicated
interactions with environment. Recent progress in our knowledge is
basicly related to technology. However, using all the tools of today's
technology, we are still unable to understand the basic normal
development. After almost thirty years of work, I am trying to present a
subjective review of the development of the human endocrine glands. I am
presenting an image emerging from my experience. I personally studied
several hundred human embryos using mostly anatomical, histochemical and
some biochemical techniques. I found much additional information in the
literature.