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

Biosynthesis

Of human

steroid

Hormones

What is the action of testosteroneWhat is the action of testosterone

Testosterone (notes)Testosterone (notes)Source

synthesized & released by Leydig (interstitial) cells of testis

release stimulated by LH

Actions

inhibits release of GnRH & LH (not FSH)

stimulates spermatogenesis (in conjunction with FSH)

stimulates differentiation of male genitalia (in utero)

stimulates development of male 2nd sexual characteristics at pubertygrowth & development of internal/external genitaliabone growth and epiphyseal plate closure, muscle developmentaxillary, pubic, body hair, male pattern baldnessfat distribution, laryngeal growth, sebaceous glandsbehavioral effects, libido, aggression

Mechanism: steroid, androgen binding protein, transcription, translation

Glycolysis , fatty acid synthesis , mineral deposition and bone growth

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

Follicular cells, corpus luteum, placenta, adrenal gland

Follicular developmentFollicular development

Estrogens synthesis by granulosa & thecal cellsEstrogens synthesis by granulosa & thecal cells

Note: “estrogens” are a mixture of estradiol (most), estriol, & estrone

LH FSH

Note: LH & FSH are shown as acting on the wrong cells in your text book

Estrogen actionsEstrogen actions

moderate increase inhibits release of GnRH & LH (negative feedback)

large increase stimulates LH release (positive feedback)

differentiation of female genitalia in utero is due to the absence of testosterone, not any actions of estrogens

stimulates the changes seen at puberty

growth of external genitalia

growth of breasts (particularly fat deposition & duct growth)

bone growth & epiphyseal plate closure (pubertal spurt & female configuration)

fat distribution, reduces LDL & raises HDL (anti-atherogenic)

during menstrual cycle

Fallopian tube peristalsis & ciliary activity, growth of myometrium & endometrium, cervical mucus abundant & clear

Lipogenesis Lipogenesis , transcription and , transcription and translation translation , ,

Progesterone actionsProgesterone actions

high levels (in presence of estrogen) inhibit release of GnRH, hence LH & FSH (negative feedback)

stimulates the changes seen at puberty

growth of breasts (particularly glandular tissue)

during menstrual cycle

Fallopian tube peristalsis & myometrial contractions

endometrial blood flow, coiling of glands, glycogen content

thick sticky cervical secretion (mucus plug)

body temperature by ~0.5 C

Note: adrenal androgens stimulate axillary & pubic hair growth, libido

Essentially required for the implantation of fertilized ovum and maintenance of pregnancy

Follicular life cycle through menstrual cycleFollicular life cycle through menstrual cycle

fig 17-17

Estrogens synthesis by granulosa & thecal cellsEstrogens synthesis by granulosa & thecal cells

fig 17-19

Note: “estrogens” are a mixture of estradiol (most), estriol, & estrone

LH FSH

Note: LH & FSH are shown as acting on the wrong cells in your text book

Implantation of blastocystImplantation of blastocyst

fig 17-24

Sequential hormonal changes during menstrual cycleSequential hormonal changes during menstrual cycle

1. degeneration of corpus luteum estrogen, progesterone, inhibin FSH & LH

2. antral follicles develop estrogen levels

3. plasma estrogen levels increase

4. ~day 7, dominant follicle secretes high levels of estrogen

5. plasma estrogen level increases sharply

6. high estrogen levels suppress FSH levels causing degeneration of non-dominant follicles

7/8. estrogen levels LH surge (positive feedback)

9. 1st meiotic division of 1 oocyte

10. ~day 14, ovulation occurs

11. the dominant follicle collapses, and reorgranizes as the corpus luteum

Sequential hormonal changes during menstrual cycleSequential hormonal changes during menstrual cycle

12. corpus luteum secretes estrogen & progesterone

13. plasma levels of estrogen & progesterone increase, suppressing release of GnRH, LH, & FSH

14. ~day 25, corpus luteum spontaneously degenerates

15. secretion & plasma levels of estrogen & progesterone

16. estrogen & progesterone FSH & LH levels which begin follicular development of the next menstrual cycle

Hormonal interactions in the femaleHormonal interactions in the female

fig 17-20

Hormonal initiation of ovulationHormonal initiation of ovulation

fig 17-21

Endometrial changes during menstrual cycleEndometrial changes during menstrual cycle

fig 17-22