Endocrinology
 The study of hormones, the endocrine
system, and their role in the physiology of
the body
The Endocrine System
 The body’s slow chemical communication
system; a set of glands that secrete
hormones into the blood stream.
Principal functions of the
endocrine system
 Maintenance of the internal environment in the
body (maintaining the optimum biochemical
environment)
 Integration and regulation of growth and
development
 Control, maintenance and instigation of sexual
reproduction, including gametogenesis, coitus,
fertilization, fetal growth and development and
nourishment of the newborn
Hormones
 A chemical released from living cells that
travels some distance to target tissues to
have a biological effect
 Secreted in very small amounts
 Transported, usually, in the blood
 Target cells have specific receptors
 Regulates cell reactions by affecting gene
expression (often gene transcription factors)
Behavioral Endocrinology
The study of the relationship between hormones
and behavior
Hormones affect behavior and behavior feeds
back to affect hormones
Hormones
↔
Behavior
Endocrine vs. Nervous System
 Major communication systems in the body
 Integrate stimuli and responses to changes
in external and internal environment
 Both are crucial to coordinated functions of
highly differentiated cells, tissues and
organs
 Unlike the nervous system, the endocrine
system is anatomically discontinuous
Hormones travel via the
bloodstream to target cells
• The endocrine system broadcasts
its hormonal messages to
essentially all cells by secretion into
blood and extracellular fluid.
• Like a radio broadcast, it requires
a receiver to get the message - in
the case of endocrine messages,
cells must bear a receptor for the
hormone being broadcast in order
to respond.
A cell is a target because it has a
specific receptor for the hormone
Most hormones circulate in the blood, coming into
contact with essentially all cells. However, a given
hormone usually affects only a limited number of cells,
which are called target cells. A target cell responds to
a hormone because it bears receptors for the
hormone.
Hormones and Behavior
Hormones DO NOT act like “faucets” in
which behavior spews forth if the
hormone spigot is open.
Hormone-behavior relationships are complex.
It is NOT appropriate to say that hormones “cause”
behavior.
Rather, hormones change the probability that a
particular behavior will be displayed in the
appropriate social context – hormones simply
influence behavior.
First endocrinology experiment
Berthold’s Experiment
1) Background: Naturalistic observations of
changes in behavior and appearance of
roosters with age and season.
2) Castrated 6 roosters.
3) Re-implanted a testis in 2 roosters.
4) Transplanted a testis from another bird in 2
roosters.
5) Left 2 castrated roosters to develop into
capons.
Normal Rooster
Normal Rooster
Capon
Major endocrine glands
The Hypothalamus
Small structure at the
base of the brain
Regulates many body
functions, including
appetite and body
temperature
Regulates the pituitary
gland
The Pituitary Gland
 A sort of master gland
 It is a cherry-sized
endocrine gland
 The hormones it
secretes affect the
growth and secretion
of other endocrine
glands
 The real boss is the
hypothalamus
Anterior and Posterior Pituitary
 Embryologically distinct
 Release different hormones
– Anterior Pituitary releases Luteinizing
hormone and growth hormone
– Posterior Pituitary releases Oxytocin
Pancreas
 Both endocrine (hormones) and exocrine
(enzymes) tissue
 Releases the hormone insulin
The Adrenal Glands
 A pair of endocrine glands just above the kidneys
 They secrete epinephrine and norepinephrine
 In common with the pituitary, adrenals are two
glands with distinct embryological origins.
– Adrenal medulla
– Adrenal cortex
 Both parts of the adrenals work
together to regulate metabolism
and cope with stress.
Sex Hormones
Sex hormones are secreted by the gonads
and by the adrenal glands
Androgens
Masculinizing hormones
Estrogens
Feminizing hormones
Gonads: Testes
 Male gonads
 Two functions
– Steroidogenic
– Gametogenic
Primary Testicular Hormones
 Steroid Hormones
– Androgens
– Estrogens
TESTOSTERONE and AGGRESSION
In most mammals, males are more aggressive, and castration reduces
aggressive behavior.
Inter-male and territorial aggression increase after puberty.
After a fight, the winner has higher, the looser lower levels of testosterone.
Criminals: Age at first violent offense correlates with testosterone levels.
Violent women prisoners have higher testosterone levels than non-violent ones.
Testosterone and Marriage
750
700
650
600
Married Once
Never Married
Remarried
Married and divorced
Gonads: Ovaries
 Female gonads
 Two compartments
– Steroidogenic
– Gametogenic
 Cyclic in function
 Hormones associated with gamete
maturation were co-opted over
evolutionary time to regulate sexual
behaviors.
Primary Ovarian Hormones
 Steroid Hormones
– Estrogens
– Progesterone
– Testosterone
The female menstrual cycle
 Consists of 3 main phases
Menses
Follicular Phase
Luteal Phase
 Each phase has differing relevant
physiological changes
Ovulation
 Ovulation has been the target of
most studies on the menstrual cycle
 Other mammals have stereotyped
sexual receptivity
 Human ovulation is “cryptic”
 Ovulation = once/month regulated
by hormones
Do women advertise fertility?





More interest in sex?
Fantasies
Clothing preferences
Gait
Topless dancer study
1
2
% feminization preferred
Menstrual Cycle
low conception risk
20%
high conception risk
15%
Significant
effect of
conception
risk
10%
5%
Penton-Voak et
al. 1999,
Nature
0%
Japanese faces Caucasian faces
Perrett et al. 1998, Nature
Feminised
Masculinised
What do women prefer?
 When ovulating, women prefer more
masculine faces.
 When not ovulating, they prefer only slightly
masculine faces.
 High estrogen women showed especially
strong shifts across the ovulatory cycle.