Good and Bad Testosterone

By Ilpo Huhtaniemi

Testosterone takes a historical approach to understanding testosterone. It is a comprehensive description of the functions of testosterone and its role in determining the biological, medical, psychological, behavioral and cultural features of the male sex/gender and the male/female differences.It is a unique reference that explains not only the biological aspects of the function of testosterone, but also the psychophysical aspects. Unlike most other hormones, testosterone not only regulates biological functions of the body, but its functions are also psychological. This wide spectrum of effects influences nearly all biological and behavioral features of a male, makes testosterone particularly exciting.Sex/gender issues are of great interest for a wide readership of experts within various disciplines and specialties including GP, gynecology, pediatrics, urology, andrology, and endocrinology.

• Discusses groundbreaking discoveries about the function of endocrine glands and hormones from the 19th century until present
• Includes information on the biology of testosterone production and its effects in men and women, including effects of high and low testosterone
• Presents male contraception with its successes and failures as well as future directions and strategies in the development of novel effective male contraceptives
• Discusses the correct, questionable and misuse of testosterone treatments

• Language: English
• Publisher: Academic Press
• Release date: Nov 6, 2023
• ISBN: 9780443134319

Ilpo Huhtaniemi

Dr Ilpo Huhtaniemi is an Emeritus Professor of Reproductive Endocrinology in the Institute of Reproductive and Developmental Biology, Imperial College London (London, UK) and Emeritus Professor of Physiology at Department of Physiology, University of Turku (Turku, Finland). His clinical specialty is in chemical pathology. He is an author of about seven hundred peer-reviewed publications as well as several book chapters on basic and clinical reproductive endocrinology and laboratory diagnosis of endocrine diseases. He currently serves as an editorial board member for several academic journals, including as editor-in-chief of Molecular and Cellular Endocrinology (Elsevier). Dr. Huhtaniemi has also edited several books in the field of reproductive endocrinology and physiology. He has received many honours for his research activities, such as the NIH International Postdoctoral Research Fellow (Fogarty Foundation), Senior Fellowship of The Academy of Finland, Young Investigator Award of The American Society of Andrology, Matti Äyräpää Award of the Finnish Medical Society DUODECIM, Honorary Membership of The Romanian Academy of Medical Sciences, Doctor h.c. of Medical University of Lodz, Poland and Doctor h.c. of Albert Szent-György Medical University, Szeged, Hungary, The Egon Diczfalusy Foundation Lifetime Achievement Award, Iain McIntyre Medal (Queen Mary University, London), and Society for Endocrinology (UK), The European Medal. Named lectures: German Endocrine Society, The Berthold Medal and Prize Lecture; Australian Society for Reproductive Biology (The Goding Lecture); Nordic Association for Andrology (The Erik Blom Lecture); The American Society of Andrology (EAA Exchange Lecture). Dr. Huhtaniemi has been elected to The Finnish Academy of Science and Letters, The Academy of Medical Sciences, UK, and he is Knight, First Class, of the Order of the White Rose of Finland.

Book preview

Chapter 1 Introduction

What makes the male a man? This question can be viewed from many angles and there are multiple alternatives. According to popular definitions, clothes make the man, or as the saying goes, the army transforms a boy into a man. There are also opinions today that the division for humans into men and women is dated. All alternatives between and outside the classical binary man-woman setting should be accepted and belong to basic human rights.

From the biological point of view, the concept of sex is quite simple. We all are genetically either males or females. The difference is whether we have in our cells two female X chromosomes which makes us women, or whether we have one X chromosome and one male Y chromosome which defines us as men. This is the starting point for the complicated process of sexual differentiation of an individual. A key role is played early in fetal life by the testis-derived testosterone in the male fetus and the lack of testosterone action in the female fetus. The end result of sexual differentiation is usually the dichotomous man-woman outcome. Occasionally, the dichotomous man-woman outcome may not be the case, but with accurate information, it becomes easier to understand and accept these variations.

Testosterone is the most important male sex hormone, of which we use the collective term androgens. From the biological point of view, the one and only function of testosterone is to make the man a psychophysical entity whose most important function, for the sake of preservation of mankind, is to continue the species. To this end, the male needs structures and functions induced by testosterone, starting early in fetal life. Testosterone is also necessary for the postnatal, pubertal, and adult stages of development. Also, the rearing in childhood, life experience, and social environment contribute to male function. Unlike most other hormones, testosterone does not only regulate biological functions of the body but its functions are also psychological. This wide spectrum of effects influencing nearly all biological and behavioral features of a male makes the scientific study of testosterone particularly exciting.

Testosterone is arguably the best-known hormone of interest to the public at large. It pops up from time to time in headings of the various forms of media, sometimes in positive, sometimes in negative light. It is the villain in doping of athletes, it provides fuel for toxic masculinity, and it plays a role in #metoo situations, violence, crimes, and rape. Quite an unpleasant hormone without which life would be much more tranquil. However, the same hormone can also make a man, in other circumstances, chivalrous, generous, protective, and strong.

Despite all progress of mankind, men are still gorillas beating their breast and predators chasing their prey. For them, the quest for dominance and competition for women against other men, as well as guarding their territory, are deeply imprinted in genes and senses. Without testosterone, men would not be psychologically and physically complete. Testosterone effects are brewing indelibly in the whole of society, culture, economy, human interactions, social status, and politics. It is associated, both at the level of individuals and nations, with success, loss, scandal, victory, and defeat. There is hardly another hormone with such a high profile. It activates all male virtues and vices, no matter how they are defined.

I have worked for about 50 years as a scientist and physician investigating the production, regulation, and effects of testosterone in cell cultures, experimental animals, and humans. I have acquired a wealth of information that has been stored in scientific publications and is not easily accessible to those outside the scientific community. It therefore occurred to me that I might have something to say to a wider audience about the knowledge and views I have acquired during my scientific career. This prompted me to write a story about the topic of my research, testosterone, this actual and mythical hormone, which is a real mover and shaker, and elixir of life, and which has so many direct and indirect actions in the life of all of us.

This book is not structured around a plot, but instead each chapter explores a different topic related to testosterone, allowing readers to approach the book in any order they choose. For this reason, some repetition could not be avoided, for which I apologize to those who intend to read the book from cover to cover.

Chapter 2 History of testosterone—From mysticism to molecule

Abstract

In this chapter, we will review the early history of the knowledge about testicular function and more generally of the male contribution to reproduction. We will review the first description of testicular structure and the discovery of the testosterone-producing testicular Leydig cells. The early animal experiments will be described, providing evidence that the testes secrete into the blood circulation a substance responsible for the male sexual function and behavior. We then describe the race between scientists in the isolation of testosterone and unraveling its structure. We will describe the discovery of the common causes of androgen deficiency (hypogonadism), and how testosterone treatment became available for the treatment of this condition. Finally, we will describe how the mechanism of androgen action was unraveled.

Keywords

Androgen receptor; Aristotle; Berthold; Butenandt; de Graaf; Laqueur; Nobel prize; Ružička; Spermatogenesis; Testosterone; van Leeuwenhoek

Thousands of years ago, as early as the stone age, people must have realized that if the testes of a male animal are removed, it becomes more docile and easier to tame and handle. The procedure also removed the boar taint from the meat of male pigs. It was also discovered that testes had a connection with reproduction because castrated male animals did not mate and produce offspring. The issue was contemplated for the first time in writing by the ancient Greek philosopher Aristotle (about 384–322 BC), who observed and described the effects of the removal of testes (further details in Chapter 19). The effects were clear and easy to describe, but the full extent of testicular function remained unknow to Aristotle. This knowledge remained obscure until the 19th century.

Ancient Greeks called the testes by name didymos or twins and the accessory organ next to testes epididymis or on top of the twins. The Latin as well as English name of the male sex gland is testis, which alludes to testifying (testimony). In ancient times, when a man took an oath, he placed his hands on top of his testes. After Aristotle's time, the scientific interest in testicular function faded for centuries.

More detailed knowledge about the structure or anatomy of the testes, as well as their function or physiology, started emerging at the time of the Golden Era of science and arts in The Netherlands in the 17th century. Reinier de Graaf (1641–73), who discovered the ovarian follicle or Graafian follicle, also studied male anatomy [1]. He described the male sex organs with detailed drawings and found out for the first time that the testes are composed of thin fluid-filled ducts, which we now know to be the seminiferous tubules. De Graaf would probably have advanced much farther in the study of male sex organs, had he not ended up with his countryman Jan Swammerdam (1637–80) in a dispute over the priority on who had discovered first the ovarian follicles. In the midst of the scientific feud, he died prematurely in obscure conditions at the age of 32 years.

Around the same time, another Dutchman, Antoni van Leeuwenhoek (1632–1723), improved the microscope, invented in the early 1600s by his countryman Zacharias Janssen (1585–1632), and started his pioneering work in microscopy. Together with medical student Johan Ham (1651–1723), using the new instrument, he observed sperm in seminal fluid. In the absence of better knowledge, he termed them little animals of the sperm [2]. van Leeuwenhoek was a self-taught scientist. By profession, he was a draper, businessman, and municipal politician, and he developed an interest in lens making. With his improved microscope, he discovered bacteria and other microorganisms and reported his findings in letters to The Royal Society of London. His microscopic findings represent a paradigm shift, as such breakthroughs are called in science.

The role of sperm in procreation still remained unclear for another 100 years, until a priest from Modena, Lazzaro Spallanzani (1629–1799), discovered their real function with artificial insemination experiments on frogs. It took another 100 years, until 1876, when the German physiologist Oscar Hertwig (1849–1922) first described the event of fertilization or penetration of the sperm into the ovum.

The testosterone-producing cells reside in the testicular space between the sperm-producing seminiferous tubules, also known as the interstitial space, and they were initially described by Franz von Leydig (1821–1908; Fig. 1) [3], a professor of zoology and comparative anatomy at the University of Würzburg. The discovery of the interstitial cells represented a side-track in the comparative anatomy studies of von Leydig. He never found out about their function, even though they still carry his name, i.e. Leydig cells. Testicular anatomy was unraveled much earlier than its function and regulation, where testosterone was found to play a pivotal role (for further details, see Chapter 3).

Fig. 1

Fig. 1 Franz von Leydig (1821–1908), the discoverer of the testicular cells-producing testosterone, nowadays termed Leydig cells. (Source: Wikimedia Commons.)

After the physicians (e.g. Hippocrates) and philosophers (e.g. Aristotle) of antiquity, and until the ascent of modern medical sciences in the 19th century, the principles of bodily functions were explained by the so-called humoral theory (humor = liquid). Accordingly, four main bodily liquids, secretion of mucous membranes (phlegm) and blood, as well as yellow and black bile, were considered to determine an individual's character and health. Human character and diseases were considered to be determined by balance between these humors. Effects of removal of the testes on psyche and the function of the body were explained quite well by the humoral theory—in the absence of more complete knowledge.

The principles of hormonal action begin to unfold

The importance of testis-derived testosterone as a regulator of male bodily functions started unfolding in the 19th century. In early animal experiments, investigators either removed the testes of experimental animals or reimplanted them in castrated animals and followed the effects of the procedures on the animals’ organ functions and behavior. In 1767, the first person to conduct such experiments with scientific accuracy was the Scottish surgeon and anatomist John Hunter (1728–93), by transplanting the testes of a cock into the abdominal cavity of a hen [4]. The transplanted testis was attached to the wall of the abdominal cavity and appeared functional, although Hunter did not report any discernible functional alterations in the recipient hen. History does not report what kind of hypotheses Hunter had when he initiated his experiments. As a surgeon, he was probably only interested in the technical feasibility and success of his experiment.

The next milestone in the discovery of testicular hormonal function was made by the German physiologist Arnold Berthold (1803–61) in 1849 [5]. He demonstrated, for the first time, that the removal of testes affected the behavior and organ functions of experimental animals, which were roosters in this case, likely due to substance(s) released by the testis to the blood stream. Castration caused atrophy of the rooster's wattle and comb and extinguished its sexual function (Fig. 2). Berthold then reimplanted testes of the same or another rooster to the abdominal cavity of a castrated rooster, or capon. The wattle and comb grew back, and male sexual function was also restored. As the transplanted tissue did not have nerve connections to the host animal, Berthold hypothesized that it must produce and secrete a factor that has a masculinizing effect into the recipient animal's circulation. This observation was groundbreaking at a time when little was known about the function of endocrine glands and the hormones they secrete into the blood stream—even the term hormone had not yet been coined. In 1905, the British physiologist Ernst Starling (1866–1927) first used the word hormone with his studies on the secretory functions of the pancreas [6].

Fig. 2

Fig. 2 Berthold's classical rooster experiment [5] . Three kinds of capons (castrated roosters) were used in the experiment. Group 1 were capons with no additional treatment, and they developed phenotype akin to females. Group 2 were capons whose removed testes were reimplanted to the abdominal cavity. They developed a male phenotype. Group 3 were capons transplanted with testes received from other roosters. They also developed male phenotype. The experiment showed that a substance secreted by the testes to the circulation, not nerve connections, brought about the male phenotype of roosters.

Berthold's experiments can be considered the beginning of modern hormone research or endocrinology, although they did not receive much attention in his own time. This lack of attention was influenced by a scientific dispute between Berthold and Rudolf Wagner (1805–64), senior to Berthold and at the time the professor of physiology at the University of Göttingen. The dispute concerned Wagner's inability to reproduce Berthold's findings. Because of Wagner's higher academic rank, influence, and scientific jealousy his opinion counted more. However, other investigators subsequently verified Berthold's findings. We have here a typical example of the self-correcting nature of scientific research: with time the truth always wins and remains. Generally accepted concepts are continuously being revised and fine-tuned with new information, and it makes the seeker of truth humble.

It took almost 90 years before the masculinizing factor produced and secreted by the testes, first discovered by Berthold, was isolated and structurally characterized. This period included a phenomenal odyssey, which was conducted by the famous French physiologist Charles-Édouard Brown-Séquard (1817–94). He treated his own aging symptoms with extracts of dog and Guinea pig testes and reported phenomenal recovery of all his aging complaints. This is such a stunning period of scientific quackery and self-deceit that it deserves to be reported in more detail in a chapter of its own (Chapter 14).

Race for isolation and unraveling the structure of testosterone

The history of natural science and medicine is reminiscent of that of voyages of discovery: multiple research groups are simultaneously competing for the same goal. It does not mean sharing a common goal but tough competition, where the stimulus is, in addition to achieving new knowledge, the quest for personal fame and prestige. In these races, as during discoveries, only the first prize is awarded.

The findings of Berthold were confirmed in several other animal species at the beginning of the 20th century. Based on these findings, a biological analytical method was even developed to determine the activity of the masculinizing factor, i.e. a bioassay. It was based on weight gain of the comb of a castrated cock or on weight gain in castrated mice or rats of the seminal vesicles, one of the androgen-dependent sex organs. When an experimental animal was treated with the masculinizing factor, i.e. a tissue extract or a serum sample, the target organ grew larger in direct proportion to the content of the factor in the sample. This method proved very useful when more definitive attempts were made for the isolation and synthesis of the male hormone [7].

At this point, it was known, based on animal experiments, that the testes secrete an unknown substance into the circulation that determines the sex-dependent physical features, functions, and behavior in men and male animals. Biochemical research methods had developed to such an extent at the beginning of the 20th century that it became possible to start isolating the hormone produced by the testis. The task was undertaken simultaneously by three research groups in Germany, Switzerland, and the Netherlands. The first worked in Göttingen, Germany, under the direction of Adolf Butenandt (1903–95). In 1929, Butenandt quickly isolated in pure form two sex hormones, estrone and pregnanediol, from mare's urine. Estrone is a female sex hormone, and pregnanediol is a metabolite of the sex hormone progesterone, a product of the corpus luteum (a hormone-producing body of the ovary) and placenta [8]. Several thousand liters of urine were needed as starting material for the isolation. Butenandt subsequently purified and identified the real pregnancy hormone progesterone in 1931 [9].

In the same year, Butenandt's group began to isolate the male hormone, using 15,000 L of urine from Berlin policemen as starting material. The end result of this isolation was a diminutive amount (15 mg) of pure crystalline hormone, for which Butenandt coined the name androsterone [9]. "Andro comes from the Greek word andras, meaning male. Stero refers to the chemical structure of four carbon rings, and one" signifies an oxygen group in the molecule. Butenandt initially believed androsterone to be the real male hormone, but it was only part of the truth.

Butenandt's observations on androsterone were confirmed at the Zürich Technical University by the Croatian chemist Leopold Ružička (1887–1976), who also managed to synthesize the androsterone molecule. This compound, however, turned out to be a weak urinary metabolite of a more potent male hormone, and so the real molecule remained undiscovered. Now Butenandt and Ružička (previously competitors) began to collaborate, where the former was sponsored by the German pharma company Schering and the latter by the Swiss company Ciba. Soon additional pharma companies joined the steroid syndicate, and with its financial support the progress accelerated [10]. This is a good example of how results can be achieved quickly through collaboration of academia and industry.

In 1935 a third group joined the race, a research team from the Dutch drug company Organon. Organon was located in the agricultural area of the south-east Netherlands, where the supply of endocrine glands from domestic animals was guaranteed. At Organon, the group of Ernest Laqueur isolated a strongly bioactive androgenic compound from 100 kg of bull testicles, for which they coined the name testosterone [11]. "Testo originated from the word testis, ster from the steroidal structure of the compound, and one" from an oxygen group (Fig. 3). Interestingly, Laqueaur predicted the structure of the new compound correctly in its name, although he did not manage to characterize its molecular structure. In fact, a similar finding on isolation of a potent male hormone-like compound was published in 1929 by two American scientists, T.F. Gallagher and Fred C. Koch [12]. Unlike Laqueur, they were hesitant to give it a name, because they had not determined its chemical structure. For this reason, their finding remained without the attention it might have deserved.

Fig. 3

Fig. 3 Structural formula of testosterone molecule (molecular weight 288).

Later the same year, Butenandt's group, in collaboration with Schering, published the structure and synthesis method of testosterone [13], and the group of Ružička published similar observations in another journal [14]. Specifically, Ružička's manuscript arrived at the journal offices on August 31st, 1935 and that of Butenandt on September 27th, 1935. This can be considered the beginning of modern male reproductive biochemistry, physiology, and pharmacology.

The groundbreaking work of Butenandt and Ružička in the field of steroid hormones was recognized soon after, and they were awarded the Nobel Prize in Chemistry in 1939. Butenandt received the prize for the isolation and structural analysis of the three types of sex hormones (estrogens, androgens, and progestins), and Ružička was rewarded for his high-quality research in the synthesis and structural analysis of steroids and some other organic compounds (terpenes). The government of Nazi Germany forced Butenandt, for political reasons, to decline the Nobel Prize because they did not accept the award of Nobel Peace Prize in 1935 to a dissident, journalist and pacifist Carl von Ossietzky (1889–1939). Neither could Ružička travel to Stockholm in late autumn 1939 to receive his prize because of the turmoil of the Second World War. Butenandt finally received his prize after the war, in 1949. However, he never received the award money because, and in accordance with the statutes of the Nobel Foundation, it must be received within 1 year of the award. Ružička was luckier since a special ceremony was organized for him in the Swedish Embassy of Bern in the beginning of 1940, where the Swedish ambassador conveyed the prize to him. Moreover, Ružička became wealthy owing to the royalties he received from the pharma industry for his discoveries and patents. Later on, he started collecting art, and he eventually donated his collection of Flemish and Dutch art to the Zürich Art Museum.

The shadow of Nazi Germany fell also on Ernest Laqueur, who was of Jewish origin. When Germany occupied The Netherlands in 1940, he lost his professorship at Amsterdam Free University and barely survived after being transported to a concentration camp. It has sometimes been wondered why he did not share the Nobel Prize with Butenandt and Ružička. After all, he had isolated testosterone and coined its name. However, unlike Butenandt and Ružička, he did not crack the structure of testosterone or synthesize the hormone, which were considered more important by the 1939 Nobel Committee in Chemistry [15]. This was achieved by the latter, who among other discoveries in steroid and organic chemistry were considered scientifically more merited. Neither was Laqueur nominated by anyone in 1939 for the Nobel Prize. Butenandt joined the Nazi Party in 1936, and it is debatable whether he tried in this way to safeguard his research facilities or whether he was a diehard Nazi. In any case, after the war, he occupied many prestigious offices and positions of trust in West Germany and died at the mature age of 88 years in 1995.

Butenandt's case was not the only one with friction between the Nazi regime and the Swedish Nobel Committee. The 1939 Nobel Prize in Physiology or Medicine was awarded to the German physician Gerhard Domagk (1895–1964), who had discovered the antibacterial sulfonamide drugs (prontosil). Domagk accepted the prize but was imprisoned for several days as punishment. Like Butenandt, he was not allowed to travel to Stockholm.

Causes and consequences of testosterone deficiency discovered; some milestones

In parallel with the development of steroid biochemistry, the knowledge about normal male reproductive functions (physiology) and diseases (pathophysiology) started unraveling. At the same time of development of the first testosterone drugs, two syndromes causing testosterone deficiency (hypogonadism) were discovered. The first one, Klinefelter syndrome, was discovered in 1942 [16] and the other, Kallmann syndrome, in 1944 [17] (more about them in Chapter 15). In both conditions the male patient suffers from lack of testosterone, and the newly discovered testosterone offered an effective means of treatment for both.

Somewhat later, in 1952, the complete lack of androgen action, termed testicular feminization (or complete androgen insensitivity syndrome, CAIS), was described [18] (more details in Chapter 19). It was later found to be caused by an inactivating mutation of the androgen receptor gene which encodes the molecule that transfers the action of testosterone and other androgens to the cellular level. Around the same time, the interest in the connection of testicular function and male aging was reawakened. A completely misleading term male menopause was coined, and still today it is difficult to get rid of it (Chapter 16).

One pioneer in clinical application of the new information about the involvement of testicular function and testosterone action in diseases was the American urologist Charles Huggins (1901–97). He observed that surgical removal of testes (castration) slows down the progression of prostate cancer [19]. For this discovery, he was awarded the Nobel Prize in 1966. The same therapeutic principle, nowadays in the form of medically induced inhibition of testosterone production, chemical castration, is still the mainstay in the treatment of advanced prostate cancer.

From molecule to medicine

Soon after unraveling of the structure and synthesis of testosterone, just before WWII broke out, the first injectable preparations of testosterone were produced. Subsequently, it was discovered that testosterone was ineffective when administered orally, the reason being its quick degradation after absorption from the gut. Injectable testosterone was initially tested for all imaginable complaints ranging from reduced sexual desire to prostatic hypertrophy. Over- and misuse of testosterone also started soon, and the first words of warning were pronounced in the 1940s. This issue will be discussed in more detail in Chapter