I have chosen Testosterone as my favourite hormone
Structure:
Steroid Hormone: A Steroid that acts as a hormone. Steroids have: 20
Carbon atoms form 4 cycloalkane rings: 3 cyclohexane rings &1 cyclopentane
ring (top ring). Steroid hormones can be
grouped into five groups by the receptors to which they bind: glucocorticoids, mineralocorticoids, estrogens, progestogens and androgens
Androgens: a compound (usually
a steroid hormone) that
stimulates/controls the development and maintenance of primary and secondary
male characteristics in vertebrates by binding to androgen receptors[Martini &
Motta, 1977].
Testosterone is a
cholesterol derivative. It is found in both males (leydig cells of the testes)
and females (placenta, ovaries, and zona reticularis of adrenal cortex. Its structure was first worked out by Adolf
Butenandt and G. Hanish in Germany [Freeman et al, 2001].
Formation Pathway:
From Cholesterol to Testosterone/DHT
Origin of
Testosterone
1767
John Hunter (a Scottish researcher) transferred
the testis of a rooster into the abdominal cavity of a hen [Freeman et al,
2001]. This produced no systemic changes
and he never publish any findings.
1849
Arnold Adolph Berthold (a German researcher) worked
on castration and testicular transplantation in roosters (cockerels) [Bendum,
1999]. This is considered one of the
first endocrine experiments. Berthold
also discovered that despite the testes being severed from the nerves, they
still had an effect on the castrated rooster [Bendum, 1999]. He then concluded that the testes must
secrete something into the blood stream.
1889
Charles-
Édouard Brown-Séquard ( a Mauritian-French researcher) spent 40 years studying
the mechanisms and effects of androgens in humans after claiming that he had
made a “rejuvenating elixir” from extracts of dog and guinea pig testicles [Brown-Séquard,
1889]. After injecting the elixir into
himself, he reported that he felt rejuvenated and that he had restored
vigor. It is widely believed that this
was mostly due to a placebo effect [Freeman et al, 2001].
1920’s
Fred C. Koch (an American researcher) established
a large supply of bovine testicles, using the Chicago stockyards and some
willing students [Freeman et al, 2001].
One of these students (Lemuel McGee) helped to isolate a substance from
the bovine testicle after pulverizing the bull testicles and using benzene and
acetone [Freeman et al, 2001]. It was
reported that this substance would remasculinize certain castrated vertebrates.
The
race to testosterone:
3 research teams competed to isolate testosterone first [Freeman et al, 2001]:
1) Organon team (in the Netherlands)
1934 & 1935: Ernst Laqueur group purified testosterone,
but couldn’t obtain large enough quantities to allow for actual human studies. The following year they wrote a paper called “On
Crystalline Male Hormone from Testicles (Testosterone)” in which they coined
the word ‘testosterone’ [Freeman et al, 2001]
2) Schering group (in Germany)
Adolf Butenandt (and
G. Hanish) worked out the structure of testosterone and published their
findings in a paper called “A Method for preparing testosterone from
Cholesterol” [Freeman et al, 2001].
3) Ciba group (in Swtizerland)
Ruzicka and A.
Wettstein published a paper called “On the Artificial Preparation of the
Testicular Hormone Testosterone (Andro-sten-3-one-17-ol), just one week after
the group from Germany [Freeman et al, 2001].
1936-1940
Androgens were discovered and Paul de Kruif
was proclaiming testosterone as an anti-aging drug [Todd, 1987].
Function
Testosterone
has organizational effects, activational effects and medical uses.
The organizational effects include gender identity,
primary sexual characteristics and brain mascularization. Gender identity is influence by testosterone
in that testosterone differentiates a normally female fetus into a male fetus[Silver
and Feder, 1979]. As Martini & Motta
discovered in 1977, primary sexual characteristics are influenced by
testosterone as well. Primary sexual
characteristics include phallic enlargement and spermatogenesis; in which the
testosterone activates the sertoli cells in order to cause the differentiation
of spermatogonia [Martini & Motta, 1977].
Brain masculinization was investigated by Mainwaring in 1977 and he
discovered that a rise in testosterone is seen in early infancy and proposed
that aromatases in the brain convert testosterone into oestradiol-17-Beta in
order for this hormone to cross the Blood-Brain Barrier and masculinize the
brain [Mainwaring, 1977]. Following more
investigations, it was also noticed that females had alpha-feroprotein which binds
estrogens so that brain masculinization could not occur [Micevych & Hammer,
1995].
The
activational effects included the activation of mating rituals and of secondary
sexual characteristics. Certain mating
rituals seen in vertebrates have a link with being performed after sexual
maturity, after the increase in testosterone has occurred. Aggression in males towards other males and
birdsong in the Oscines bird group are two of the mating rituals that are
linked with increases in testosterone [Micevych & Hammer, 1995]. Silver and Feder studied the activation of
secondary sexual characteristics by
testosterone. They found that
testosterone activates a wide variety of characteristics, such as the vocal
deepening, and the growth of muscle,
bones, hair, sebaceous glands and the Adam’s Apple[Silver and Feder, 1979].
The
medical applications that testosterone has includes prevention of Osteoporosis,
Alzheimer’s Disease, Type 2 Diabetes and Hypogonadism [Schulster et al, 1976]. High concentrations of testosterone can also
help with athletic performance [Todd, 1987] and sexual libido[Silver and Feder,
1979].
References
Benedum, Jost
(1999) The early history of endocrine cell transplantation. Journal of Molecular Medicine. Vol 77. 1. pages
30-35, DOI: 10.1007/s001090050296
Brown-Séquard C. E. (1889). "The effects
produced on man by subcutaneous injection of a liquid obtained from the
testicles of animals". Lancet 137:105–107. Found at http://www.usrf.org/news/TRT/Brown- Sequard,%20Lancet,%201889.pdf.
Freeman, Erica F., Bloom, David
A., Mcguire, Edward J. (2001) A Brief History of Testosterone. The
Journal of Urology. vol 165, issue 2, pages 371- 373, issn 0022-5347,
10.1097/00005392-200102000-00004.
Mainwaring, W.I.P (1977) The Mechanism of Action of
Androgens. Springer-Verlag New York
Inc. pg.32-41
Martini, Luciano & Motta, Marcella (1977) Androgens
and Antiandrogens. Raven Press New
York. Pg.1-14, 37-54, 67-73, 120-146, 299-301.
Micevych, Paul, E., Hammer, Ronald, P. (1995).
Neurobiological Effects of Sex Steroid Hormones. Cambridge University Press. Pg.297- 304
Mortimer, B. C. (1995) Features of Cholesterol
Structure That Regulate the Clearance of Chylomicron-like Lipid Emulsions.
Journal of lipid research. Vol 36. Issue 9. Page 2038. ISSN: 0022-2275
Schulster, D., Burstein, S., Cooke, Brian, A., (1976). Molecular
Endocrinology of the Steroid Hormones. John Wiley & Sons Ltd. Pg 134-136
Silver, Rae, Feder, Harvey, H. (1979) Scientific
American. Hormones and Reproductive Behavior. W.H. Freeman and Company. Page 49
Todd,T. (1987) Anabolic Steroids: The Gremlins of
Sport. Journal of sport history. Vol 14. Issue 1. Page 87-107. ISSN: 0094-1700.
