Location of the Endocrine Glands
Endocrinology:
- The study of biological messaging or signaling ______
- Endo = ______; crine = ______
Endocrine glands secrete hormones directly → _________ → ______ cells
- Pituitary, thyroid, parathyroid, adrenal, pineal, gonads
____________ = master switchboard; part of brain that controls the endocrine system
- The study of biological messaging or signaling molecules
- Endo = internal; crine = secrete
Endocrine glands secrete hormones directly → bloodstream → target cells
* Pituitary, thyroid, parathyroid, adrenal, pineal, gonads
Hypothalamus = master switchboard; part of brain that controls the endocrine system
Location of the Endocrine Glands
Certain organs and tissues contain endocrine tissue and also ______ ______:
* Hypothalamus, thymus, pancreas, ovaries, testes, kidneys, stomach, liver, small
intestine, skin, heart, adipose tissue, placenta
- Endocrine + nervous system = _____-______ system
Certain organs and tissues contain endocrine tissue and also secrete hormones:
* Hypothalamus, thymus, pancreas, ovaries, testes, kidneys, stomach, liver, small
intestine, skin, heart, adipose tissue, placenta
- Endocrine + nervous system = neuro-endocrine system
Pituitary Gland: “the Hypophysis” or “Master Gland”
* most highly _______ system in the body
* controls endocrine glands
Hypothalamus and pituitary work together to control and coordinate:
* met…..
* G and M
* repr….
* homeo….
- most highly vascularized system in the body
- controls endocrine glands
Hypothalamus and pituitary work together to control and coordinate:
* metabolism
* growth and maturation
* reproduction
* homeostasis
The Master Gland: The Pituitary
2 distinct lobes:
* ______ & ______
____ pituitary is the “master” gland:
* Produces ___ primary hormones
* Source of G and M
- Hypothalamus is the source of releasing _____ (RF) or releasing _______ (RH)
- Growth hormone (GH) also known as ______
The Master Gland: The Pituitary
2 distinct lobes:
* Anterior & Posterior
Anterior pituitary is the “master” gland:
* Produces 6 primary hormones
* Source of growth and metabolism
- Hypothalamus is the source of releasing factors (RF) or releasing hormones (RH)
- Growth hormone (GH) also known as somatotropin
Tropic Hormones (Targets are other Endocrine Glands)
- TSH
* (thyrotropin) - ACTH
* (corticotropin) - GT (2)
* follicle stimulating hormone (FSH)
* luteinizing hormone (LH) - GH (tropic and directly acting)
* (somatotropin)
- _______ is not a tropic hormone
- Thyroid stimulating hormone
* (thyrotropin) - Adrenocorticotropic hormone (ACTH)
* (corticotropin) - Gonadotropins (2)
* follicle stimulating hormone (FSH)
* luteinizing hormone (LH) - Growth Hormone (tropic and directly acting)
* (somatotropin)
- Prolactin is not a tropic hormone
Neuro-Endocrine Regulation of Growth and Maturation
- CNS Hypothalamus
- Anterior pituitary
- Target glands, examples of (4)
- Target tissues, examples of (4)
- Target tissue hormone, examples of (4)
Target gland
* Thyroid
* Adrenals
* Liver
* Gonads
Target Tissues
* Muscle
* Bone
* Fat
* Reproductive
Target Tissue Hormones
* IGF-1
* Androgens
* Sex steroids
* Growth factor
Example of Feedback Control Mechanisms (look at slide 15)
Specific releasing hormone:
GHRH = growth hormone releasing hormone
-short feedback loop
Tropic hormone for specific gland
Target gland (e.g., liver)
- Long feedback loop to hypothalamus and anterior pituitary
Target gland releases hormone
Target tissues with appropriate receptors → hormone action
Overview of Neuroendocrine Regulation of Growth - slide 16
Liver: ____
Thyroid: _____, _____
Adrenal cortex: Gluco…., Mineral…., _____ steroids (test/est/prog & precursors)
Ovaries: _____, ______
* most _____ from ovaries
Testes: _______
* most ______ from testes
Liver: IGF-1
Thyroid: thyroxin, triiodohyronine
Adrenal cortex: Glucocorticoids, Mineralocortocoids, Anabolic steroids (test/est/prog & precursors)
Ovaries: estradiol, progesterone
* most estradiol from ovaries
Testes: testosterone
* most testosterone from testes
Endocrine Control of Menstrual Cycle
Follicular phase:
* Estrogen & progesterone are _______
* ______ occurs
- Anterior pituitary increases _____ production
→ stimulates growth of _______ (each contains an egg) - Follicles produce ______ → stimulates LH
- LH surges, causing follicle to ______ and release _____ (‘ovulation’)
Follicular phase:
* Estrogen & progesterone are low
* Menstruation occurs
- Anterior pituitary increases FSH production
→ stimulates growth of follicles (each contains an egg) - Follicles produce estrogen → stimulates LH
- LH surges, causing follicle to rupture and release egg (‘ovulation’)
Endocrine Control of Menstrual Cycle
Luteal phase (after ovulation):
- Ruptured follicle closes after releasing egg → CL
- Produces ____________
- Prepares uterus for implantation of ______
- If egg isn’t fertilized or doesn’t implant, CL degenerates after ___ days
- ________ decreases and new menstrual cycle begins
“estrogen primes ________”
- Ruptured follicle closes after releasing egg → corpus luteum
- Produces progesterone
- Prepares uterus for implantation of embryo
- If egg isn’t fertilized or doesn’t implant, corpus luteum degenerates after 14 days
- Progesterone decreases and new menstrual cycle begins
“estrogen primes progesterone”
Sequence of Events:
Endocrine Control of Menstrual Cycle
1. GnRH stimulates __________ gland to release _____
- ______ stimulates growth of follicles
- Follicles produce ________
- _______ stimulates _______ to release surge of ______
- ____ surge causes follicle to rupture
- Corpus luteum produces _________
Menopause?
How do Hormonal Contraceptives Work?
- Based on what you know about the menstrual cycle, how might hormonal contraceptives (birth control) affect the menstrual cycle?
- GnRH stimulates Anterior pituitary gland to release FSH
- FSH stimulates growth of follicles
- Follicles produce estrogen
- Estrogen stimulates hypothalamus/anterior pituitary to release surge of LH
- LH surge causes follicle to rupture
- Corpus luteum produces progesterone
- estrogen down, FSH up
- Pill = e and p, you never get the low to reach fsh
Hypothalamus-Pituitary-Growth Axis
* Growth hormone: regulation of ______ growth
* General, _______ growth effects
How does the hypothalamus-pituitary-growth axis regulate growth?
Hypothalamus-Pituitary-Growth Axis
Direct action (anabolic):
* Growth of all ______ in the body (e.g., bone, muscle)
* GH levels rise during ______, peak during _____
* Regulated by GHRH produced by _______
Tropic (targets other glands):
* Stimulates _____ to produce. ……(IGF-1)
* IGF-1 simulates growth in many body ____
- GH and IGF-1 are major regulators of growth from ~ ____ year to puberty
- Growth hormone: regulation of somatic growth
- General, widespread growth effects
Stimulating hypothalamus to release GHRH in ant pituatry and acts on cells and GHIH and feedback loop
Direct action (anabolic):
* Growth of all tissues in the body (e.g., bone, muscle)
* GH levels rise during childhood, peak during puberty
* Regulated by GHRH produced by hypothalamus
Tropic (targets other glands):
* Stimulates liver to produce insulin-like growth factor (IGF-1)
* IGF-1 simulates growth in many body tissues
- GH and IGF-1 are major regulators of growth from ~ 1 year to puberty
Growth Hormone
* A ______ hormone
- highest in the first ___ hrs of sleep
* ________ (min. by min.) levels
* Breaks down in _____
* Levels respond to what 3 things
Growth Hormones and Growth Velocity - look at slide 29
* IGF-1 gene mutations disrupt in ____ & _____ growth
* GH mutations primarily disrupt ______ growth
* During puberty, sex hormones promote _____ secretion
- A nocturnal hormone
- highest in the first 2 hrs of sleep
- Fluctuating (min. by min.) levels
- Breaks down in minutes
- Levels respond to sleep, nutrition, stress
- IGF-1 gene mutations disrupt in utero & postnatal growth
- GH mutations primarily disrupt postnatal growth
- During puberty, sex hormones promote GH secretion
Hypothalamus-Pituitary-Gonadal (HPG) Axis
- At puberty, hypothalamus increases production of …..(GnRH)
- GnRH triggers release of _____ and ______ from anterior pituitary
- What controls the timing of puberty?
Hypothalamus → anterior pituitary → Gonadal axis
(Gonadotropin RH) (FSH & LH)
- LH and FSH travel through bloodstream to _____
- FSH → _________________
- LH → stimulates Leydig cells in testicles → _____________
- _______ feedback loop to pituitary and hypothalamus
- At puberty, hypothalamus increases production of gonadotropin-releasing hormone (GnRH)
- GnRH triggers release of LH and FSH from anterior pituitary
*Don’t fully know but think neurotransmitters block GnRh and then unnblocks in puberty. Leads to increase in testis size for men and breast size woman. Puberty blockers = GnRh agonists
- LH and FSH travel through bloodstream to gonads
- FSH → spermatogenesis
- LH → stimulates Leydig cells in testicles → testosterone
- Negative feedback loop to pituitary and hypothalamus
Hypothalamus-Pituitary-Gonadal (HPG) Axis
Spermatogenesis:
* ______ spermatogonia differentiate into ______ spermatozoa
* Continual process from ______ onwards
* Spermatogenic cycle (production → maturation) ~ ____ to ____ days
Trends in Male Adult Fertility
- Sperm count is declining at an ________ pace globally
- Diploid spermatogonia differentiate into haploid spermatozoa
- Continual process from puberty onwards
- Spermatogenic cycle (production → maturation) ~ 60 to 90 days
- Sperm count is declining at an accelerated pace globally (sperm/ml), from 101 to 49 million/ml
Sperm Health
* 1/5 issues with fertility due to sperm _____
Factors that affect sperm quality:
* A____
* H______
* Environmental ______
* A______/S_______
READ
Hypothalamus-Pituitary-Gonadal Axis (Males) - look at slides 36-37
- Transient HPG activation at ages 2-3
- Suppressed levels during early and mid- childhood (ages 3-8)
- Slowly rising levels during early puberty. Most drastic increases mid- puberty (8-20)
Hypothalamus-Pituitary-Gonadal Axis (Females)
- Rise in genestation
- Suppressed levels during early and mid- childhood (birth till age 8)
- Slowly rising levels during early puberty. Most drastic increases mid- puberty (age 8-20)
- 1/5 issues with fertility due to sperm quality
Factors that affect sperm quality: - Age
- Heat
- Environmental toxins
- Alcohol/smoking
Sex Steroids in Males and Females across the Lifespan - slide 38
Estrogen and testosterone are present in both sexes
Fetal: sex steroids are present and help guide development.
Infancy: brief early hormone surge, then levels fall.
Childhood: very low sex steroid levels in both sexes.
Puberty: sharp rise, mainly testosterone in males and estradiol in females.
Reproductive years: hormones stay high to support adult reproductive function.
Post-menopause/older age: female estradiol drops sharply at menopause, male testosterone declines more gradually
Adrenal Androgens and Adrenarche
Hypothalamus -> Pituitary -> Adrenal Axis (HPA):
(Corticotropin RF) (Adrenocorticotropic Hormone, ACTH)
Responsible for:
* Pre-pubertal increases in ____ in both sexes.
Secondary sex characteristics:
* ___ hair and _____ hair
* Additive to _____ testosterone and ______ increases at puberty
- _____ and ___ production
Adrenal activation (5–8-years-old): _______ (awakening of adrenal glands)
- Pre-pubertal increases in fat in both sexes.
Secondary sex characteristics: - Pubic hair and facial hair
- Additive to gonadal testosterone and estrogen increases at puberty
- DHEA and DHEAS production (sweat, acne/oils, facial and pubic hair, body odor)
Adrenal activation (5–8-years-old): Adrenarche (awakening of adrenal glands)
Adrenal Androgens and Adrenarche
Adrenal activation (5–8-years-old):
* Development and maturation of ______ ______
- Increased secretion of ______ prohormones (mainly DHEA, DHEA-S), plus
small amounts of ______ steroids (testosterone and estrogen) - Adrenal pro-hormones converted to sex steroid in most somatic (especially fat)
tissues if enzyme _______ is present - Low fat levels → lower ____ _____ levels in pre-puberty
Adrenal activation (5–8-years-old):
* Development and maturation of Adrenal Cortex
- Increased secretion of androgen prohormones (mainly DHEA, DHEA-S), plus
small amounts of sex steroids (testosterone and estrogen) - Adrenal pro-hormones converted to sex steroid in most somatic (especially fat)
tissues if enzyme aromatase is present - Low fat levels → lower sex steroid levels in pre-puberty
Summary Sources of Androgens & Sex Steroids
_____:
* Prohormone androgens and large amounts of testosterone/estrogen
_____ _____:
* Prohormone androgens and small amounts of testosterone and estrogen
________ _____ cells:
* Limited intrinsic prohormone production, but site of conversion of circulating prohormones to estrogen
- Prohormone androgens and large amounts of testosterone/estrogen
Adrenal Glands:
* Prohormone androgens and small amounts of testosterone and estrogen
Subcutaneous fat cells:
* Limited intrinsic prohormone production, but site of conversion of circulating prohormones to estrogen
Changes in Growth Hormones During Puberty - slide 45
* Peak _____ coincides with peak growth velocity
* ______-1 pattern similar to that for ____
* Decreases in both ____ and ______-1 after growth spurt in both sexes
* Similar relationship between peaks in____/_____ and height/BMC velocities in boys
Hormones and Stages of Growth
Predominance of specific systems at different stages of growth
Sex steroids during adolescence stimulate:
* ______ growth
* Ske….. maturity
* Sex… maturity
Childhood:
* GH
* Liver ……
Adolescence:
* Gonadal ____ ___
* GH
* Liver ….
- Peak GH coincides with peak growth velocity
- IGF-1 pattern similar to that for GH
- Decreases in both GH and IGF-1 after growth spurt in both sexes
- Similar relationship between peaks in GH/IGF-1 and height/BMC velocities in boys
- Somatic growth
- Skeletal maturity
- Sexual maturity
Childhood:
* Growth hormone
* Liver IGF-1
Adolescence:
* Gonadal sex steroids
* Growth hormone
* Liver IGF-1
Puberty in Humans: Two Developmental Processes
_______:
* Maturation of adrenal cortex and its production of adrenal androgens (pro-hormones)
->
_______
* Pubic hair / body hair
* Body odor
* Acne
Gonadarche: Independent of Adrenarche
* Maturation of ovaries and testes:
1. Production of _____ sex steroids (primarily estrogen in females, testosterone in males)
2. Completion of gametogenesis
* ____ in females
* ____ in males
Also contributes to growth of primary sex _____ and ____ growth (muscle and bone tissue!)
Adrenarche:
* Maturation of adrenal cortex and its production of adrenal androgens (pro-hormones)
->
Pubarche
* Pubic hair / body hair
* Body odor
* Acne
Gonadarche: Independent of Adrenarche
* Maturation of ovaries and testes:
1. Production of gonadal sex steroids (primarily estrogen in females, testosterone in males)
2. Completion of gametogenesis
* Eggs in females
* Sperm in males
Also contributes to growth of primary sex organs and somatic growth (muscle and bone tissue!)
Timing of Human Puberty
Pubertal Timing:
* In boys: rarely before ___ years of age; late if no signs by ____ years
* In girls: rarely before ___ years of age; usually by ___ years; late if no thelarche
(breast budding) by ____ years or amenorrheic after ___ years
- In boys: rarely before 9 years of age; late if no signs by 14 years
- In girls: rarely before 8 years of age; usually by 13 years; late if no thelarche
(breast budding) by 13 years or amenorrheic after 15 years
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Intro to Growth32
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Study design14
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Growth charts part 110
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Growth charts part 224
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Post natal growth (after midterm)27
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Weight-neutral approaches to health (Guest lecture)1
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Prenatal part 122
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Prenatal part 226
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Prenatal part 315
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Sex Determination11
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Endocrine23
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Biological Maturation35
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Skeletal System30
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Growth Injuries13
