EndocrinologyEndocrinology

The study of hormones, the endocrine The study of hormones, the endocrine system, and their role in the physiology of system, and their role in the physiology of the body the body

The Endocrine SystemThe Endocrine System

The body’s slow chemical communication The body’s slow chemical communication system; a set of glands that secrete system; a set of glands that secrete hormones into the blood stream.hormones into the blood stream.

Principal functions of the Principal functions of the endocrine systemendocrine system

Maintenance of the internal environment in the Maintenance of the internal environment in the body (maintaining the optimum biochemical body (maintaining the optimum biochemical environment)environment)

Integration and regulation of growth and Integration and regulation of growth and developmentdevelopment

Control, maintenance and instigation of sexual Control, maintenance and instigation of sexual reproduction, including gametogenesis, coitus, reproduction, including gametogenesis, coitus, fertilization, fetal growth and development and fertilization, fetal growth and development and nourishment of the newbornnourishment of the newborn

HormonesHormones

A chemical released from living cells that A chemical released from living cells that travels some distance to target tissues to travels some distance to target tissues to have a biological effecthave a biological effect Secreted in very small amountsSecreted in very small amounts Transported, usually, in the bloodTransported, usually, in the blood Target cells have specific receptorsTarget cells have specific receptors Regulates cell reactions by affecting gene Regulates cell reactions by affecting gene

expression (often gene transcription factors)expression (often gene transcription factors)

Behavioral EndocrinologyBehavioral 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 SystemEndocrine vs. Nervous System Major communication systems in the bodyMajor communication systems in the body Integrate stimuli and responses to changes Integrate stimuli and responses to changes

in external and internal environmentin external and internal environment Both are crucial to coordinated functions of Both are crucial to coordinated functions of

highly differentiated cells, tissues and highly differentiated cells, tissues and organsorgans

Unlike the nervous system, the endocrine Unlike the nervous system, the endocrine system is anatomically discontinuoussystem is anatomically discontinuous

Hormones travel via the Hormones travel via the bloodstream to target cellsbloodstream 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 A cell is a target because it has a specific receptor for the hormonespecific 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 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.

HormonesHormones and Behaviorand Behavior

First endocrinology experimentFirst endocrinology experiment

Berthold’s ExperimentBerthold’s Experiment

1)1) Background: Naturalistic observations of Background: Naturalistic observations of changes in behavior and appearance of changes in behavior and appearance of roosters with age and season.roosters with age and season.

2)2) Castrated 6 roosters.Castrated 6 roosters.

3)3) Re-implanted a testis in 2 roosters.Re-implanted a testis in 2 roosters.

4)4) Transplanted a testis from another bird in 2 Transplanted a testis from another bird in 2 roosters.roosters.

5)5) Left 2 castrated roosters to develop into Left 2 castrated roosters to develop into capons.capons.

Normal Rooster Normal Rooster Capon

Major endocrine glandsMajor endocrine glands

The HypothalamusThe Hypothalamus

Small structure at Small structure at the base of the the base of the brain brain

Regulates many Regulates many body functions, body functions, including appetite including appetite and body and body temperaturetemperature

Regulates the Regulates the pituitary glandpituitary gland

The Pituitary GlandThe Pituitary Gland

A sort of master A sort of master glandgland

It is a cherry-sized It is a cherry-sized endocrine glandendocrine gland

The hormones it The hormones it secretes affect the secretes affect the growth and growth and secretion of other secretion of other endocrine glandsendocrine glands

The real boss is the The real boss is the hypothalamushypothalamus

Embryologically distinct Embryologically distinct Release different hormonesRelease different hormones

– Anterior Pituitary releases Luteinizing Anterior Pituitary releases Luteinizing hormone and growth hormonehormone and growth hormone

– Posterior Pituitary releases OxytocinPosterior Pituitary releases Oxytocin

Anterior and Posterior PituitaryAnterior and Posterior Pituitary

PancreasPancreas Both endocrine (hormones) and exocrine Both endocrine (hormones) and exocrine

(enzymes) tissue(enzymes) tissue Releases the hormone insulinReleases the hormone insulin

The Adrenal GlandsThe Adrenal Glands

A pair of endocrine glands just above the A pair of endocrine glands just above the kidneyskidneys

They secrete epinephrine and norepinephrine They secrete epinephrine and norepinephrine In common with the pituitary, adrenals are two In common with the pituitary, adrenals are two

glands with distinct embryological origins.glands with distinct embryological origins.– Adrenal medullaAdrenal medulla– Adrenal cortexAdrenal cortex

Both parts of the adrenals work Both parts of the adrenals work together to regulate metabolism together to regulate metabolism and cope with stress.and cope with stress.

Sex HormonesSex Hormones

Sex hormones are secreted by the Sex hormones are secreted by the gonads and by the adrenal glandsgonads and by the adrenal glands

AndrogensAndrogens

Masculinizing hormonesMasculinizing hormones

EstrogensEstrogens

Feminizing hormonesFeminizing hormones

Gonads: TestesGonads: Testes

Male gonadsMale gonads Two functionsTwo functions

– SteroidogenicSteroidogenic– GametogenicGametogenic

Primary Testicular HormonesPrimary Testicular Hormones

Steroid HormonesSteroid Hormones– AndrogensAndrogens– EstrogensEstrogens

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 TESTOSTERONE and AGGRESSIONAGGRESSION

600

650

700

750

Married Once Remarried

Never Married Married and divorced

Testosterone and MarriageTestosterone and Marriage

Gonads: OvariesGonads: Ovaries Female gonadsFemale gonads Two compartmentsTwo compartments

– SteroidogenicSteroidogenic– GametogenicGametogenic

Cyclic in functionCyclic in function Hormones associated with gamete Hormones associated with gamete

maturation were co-opted over maturation were co-opted over evolutionary time to regulate evolutionary time to regulate sexual behaviors.sexual behaviors.

Primary Ovarian HormonesPrimary Ovarian Hormones

Steroid HormonesSteroid Hormones– EstrogensEstrogens– ProgesteroneProgesterone– TestosteroneTestosterone

The female menstrual cycleThe female menstrual cycle

Consists of 3 main phasesConsists of 3 main phases

Menses Menses

Follicular PhaseFollicular Phase

Luteal PhaseLuteal Phase Each phase has differing relevant Each phase has differing relevant

physiological changesphysiological changes

OvulationOvulation

Ovulation has been the target of Ovulation has been the target of most studies on the menstrual cyclemost studies on the menstrual cycle

Other mammals have stereotyped Other mammals have stereotyped sexual receptivitysexual receptivity

Human ovulation is “cryptic”Human ovulation is “cryptic” Ovulation = once/month regulated Ovulation = once/month regulated

by hormonesby hormones  

      

Do women advertise fertility?Do women advertise fertility?

More interest in sex?More interest in sex? Fantasies Fantasies Clothing preferencesClothing preferences GaitGait Topless dancer studyTopless dancer study

1 2

Menstrual Cycle Menstrual Cycle

Penton-Voak et al. 1999, Nature

0%

5%

10%

15%

20%

Japanese faces Caucasian faces

% f

emin

izat

ion

pre

ferr

ed low conception risk

high conception risk Significant effect of conception risk

Feminised Masculinised

Perrett et al. 1998, Nature

What do women prefer?What do women prefer?

When ovulating, women prefer more When ovulating, women prefer more masculine faces.masculine faces.

When not ovulating, they prefer only slightly When not ovulating, they prefer only slightly masculine faces.masculine faces.

High estrogen women showed especially High estrogen women showed especially strong shifts across the ovulatory cycle.strong shifts across the ovulatory cycle.