Reproductive hormones Flashcards
Peptide hormones:
1. Synthesis
2. Storage
3. Release from parent cell
4. Transport in blood
5. Half-life
6. Receptor location
7. Response to receptor ligand binding
8. General target response
9. Examples
- Made in advance
- Stored in secretory vesicles
- Exocytosis
- Dissolved in plasma
- Short
- Cell membrane (ex. GPCR)
- Activation of second messenger systems (may active genes)
- Modification of existing proteins and induction of new protein synthesis
- Insulin, parathyroid hormone, LH, FSH, GnRH
Steroid Hormones:
- Synthesis
- Storage
- Release from parent cell
- Transport in blood
- Half-life
- Receptor location
- Response to receptor ligand binding
- General target response
- Examples
- Synthesized on demand from precursors
- Not stored
- Simple diffusion
- Bound to carrier proteins
- Long
- In cytoplasm or nucleus (some may have membrane receptors)
- Activation of genes for transcription and translation (may have non genomic actions)
- Induction of new protein synthesis
- Aldosterone, estrogen, testosterone, progestin
Thyroid hormones synthesis and storage
Synthesized on demand from stored precursors
Trophic Hormone
1. Location
2. Primary target
3. Main effects
- Hypothalamus
- Anterior pituitary
- Release or inhibit pituitary hormones
Oxytocin
1. Location
2. Primary target
3. Main effects
- Posterior pituitary
- Breast and uterus
- Milk ejection, labour and delivery, behaviour
Vasopressin (ADH)
1. Location
2. Primary target
3. Main effects
- Posterior pituitary
- Kidney
- Water reabsorption
Prolactin
1. Location
2. Primary target
3. Main effects
- Anterior pituitary
- Breast
- Milk production
Growth Hormone (somatotropin)
1. Location
2. Primary target
3. Main effects
- Anterior pituitary
- Liver, many tissues
- Growth factor secretion, growth and metabolism
Corticotropin (ACTH)
1. Location
2. Primary target
3. Main effects
- Anterior pituitary
- Adrenal cortex
- Cortisol release
Thyrotropin (TSH)
1. Location
2. Primary target
3. Main effects
- Anterior pituitary
- Thyroid gland
- Thyroid hormone synthesis
Follicle-stimulating hormone (FSH)
1. Location
2. Primary target
3. Main effects
- Anterior pituitary
- Gonads
- Egg or sperm production: sex hormone production
Luteinizing Hormone (LH)
1. Location
2. Primary target
3. Main effects
- Anterior pituitary
- Gonads
- Sex hormone production: egg or sperm production
Androgens
1. Location
2. Primary target
3. Main effects
- Testes (male)
- Many tissues
- Sperm production, secondary sex characteristics
Inhibin (males)
1. Location
2. Primary target
3. Main effects
- Testes (male)
- Anterior pituitary
- Inhibits FSH secretion
Estrogen/Progesterone
1. Location
2. Primary target
3. Main effects
- Ovaries (female)
- Many tissues
- Egg production, secondary sex characteristics
Inhibin (females)
1. Location
2. Primary target
3. Main effects
- Ovaries
- Anterior pituitary
- Inhibits FSH secretion
Relaxin
1. Location
2. Primary target
3. Main effects
- Ovaries
- Uterine muscle
- Relaxes muscle
(Hormone during pregnancy)
Estrogen/Progesterone during pregnancy
1. Location
2. Primary target
3. Main effects
- Placenta
- Many tissues
- Fetal, maternal development
Chorionic somatomammotropin during pregnancy
1. Location
2. Primary target
3. Main effects
- Placenta
- Many tissues
- Metabolism
Chorionic gonadotropin during pregnancy
1. Location
2. Primary target
3. Main effects
- Placenta
- Corpus luteum
- Hormone secretion
What kind of hormones control the secretion of other hormones
Release hormones
What are tropic hormones and where are they found
Tropic hormones target another endocrine gland/cell to control hormone release
Found in hypothalamus (neurohormones) and anterior pituitary (hormones)
Dopamine pathway
Dopamine-> prolactin-> target= breast
Thyroid releasing hormone pathway
TRH-> Thyroid stimulating hormone (TSH)-> thyroid gland release thyroid hormones-> target=many tissues
Corticotropin releasing hormone pathway
CRH-> (ACTH) adrenocorticotropic hormone-> adrenal cortex releases cortisol-> target= many tissues
Growth hormone releasing hormone pathway
GHRH-> GH-> liver releases insulin like growth factors (IGFs)-> target= many tissues
Gonadotropin releasing hormone pathway
GnRH-> FSH or LH -> endocrine cells of the gonads-> androgens (male) or estrogen/progesterone (female) -> germ cells of gonads (male) and many tissues (both)
How can GnRH target FSH and LH
GnRH secretion is pulsatile
What do LH and FSH stand for
Luteinizing hormone and follicle stimulating hormone
What kind of hormone is progesterone
20C steroid hormone
What kind of hormone is testosterone
19C steroid hormone
Where receptors to progesterone and testosterone bind to
Progesterone receptor and androgen receptor
Estradiol 17 Beta type of hormone and receptor
19C steroid hormone
Estrogen receptor
Where are steroid receptors found and what is their action (general)
Intracellular and act by regulating gene expression
What size of glycoprotein is FSH vs LH
FSH 28 kDa
LH 33 kDa
Both use GPCRs
Name the three important parts of the anterior pituitary
- Parvicellular neurosecretory cells
- Median eminence
- Hypothalamohypophyseal portal vessels
Name the important cells for the posterior pituitary
Magnocellular neurosecretory cells
Key notes for posterior pituitary
Release site not production site
Neural tissue- neurohormones
Extension of hypothalamus
Role of magnocellular neurosecretory cells
Hypothalamic cells
Big
Synthesize hormones that are released by posterior pituitary
Role of parvicellular neurosecretory cells
Hypothalamic cells
Small
Project to median eminence
Role of median eminence
Start of portal system
What is the portal system
Start with capillaries and end with capillaries
Doesn’t pass through the heart
Delivers hormones
Role of hypothalamohypophyseal portal vessels
Messenger, delivery system
What do gonadotropes produce
Gonadotropins- FSH and LH
What do lactotropes produce
Prolactin
What converts cholesterol to pregnenolone and what type of reaction is it
Cytochrome-P450 (CYP450)
Redox reaction
What is the master precursor for sex steroid hormones
Pregnenolone
What type of cells produce the sex steroid hormones
Steroidogenic cells
What can steroidogenic cells do and what do they have (3)
- have lipid droplets
- have lots of smooth ER to store lipids
- ability to take up circulating cholesterol (usually by LDL or VLDL)
Name the three sex steroid hormones
Progesterone
Testosterone
Estrogen (specifically estradiol 17beta)
What is the main androgen and where is it produced
Testosterone
Produced in the testes
What keeps testosterone high in the testes
ABP- androgen binding protein that keeps testosterone in the testes
—Essential for sperm production
Role of progesterone
Maintain uterine lining (endometrium)
Role of cortisol
Important for mobilization of glucose
Stress hormone
Maintain high energy levels
What converts testosterone to estradiol 17B
Aromatase
What converts testosterone to dihydrotestosterone (DHT)
5alpha-reductase
Role of DHT
T Converted to DHT during puberty
DHT develops male characteristics
Dependent on 5alpha reductase active/healthy
What does 5alpha-reductase do
T -> DHT (dihydrotestosterone)
What does aromatase do
Testosterone -> estradiol 17B
Peripheral conversion
When is pregnenolone modified
Before leaving the cell
Steroid hormones are not regulated at the level of secretion
When does regulation occur
Level of uptake, mobilization and synthesis of cholesterol
Level of steroidogenic enzyme expression
Where can you find steroidogenic enzymes
Inner mitochondrial membrane
Membrane of SER
Where is the total hormone production coming from
Equal to sum of secretion of hormone from steroidogenic cell and peripheral conversion from another type of steroid
How do steroid hormones circulate
Bound to carrier proteins
(Sex hormone binding globulin SHBG)
What is the role of receptors
receptor determines which cells will respond
Explain hydrophobic/lipophilic qualities of sex steroids
-Readily pass through cell membranes
-poorly soluble in blood
-lipophilic binding proteins
Name 2 lipophilic binding proteins
Albumin
SHBG- sex hormone binding globulin
Explain storage for sex steroids
Not stored (diffuse easily)
Large secretory capacity
How can we deliver sex steroids to a patient
Orally- easy to absorb
GI absorption
How are sex steroids excreted
Liver breaks down hormones causing inactivation. conjugation (glucuronides or sulphate conjugation) improves hormone water solubility allowing excretion by kidneys
What does peripheral conversion do
Converts hormone A to hormone B
Action of sex steroids
Regulate gene expression
Mechanism for sex steroid action
Hormone diffuse into cell
Bind to intracellular receptor
Translocate into nucleus
Regulate gene expression
Name some factors influencing sex steroid level/function
- Cholesterol levels
- binding protein mutation/issue
- receptor issue
- feedback hormones
- peripheral conversion activity
- Excretion amount
- steroid supplements
-age, menopause, sex
Explain hydrophilic/soluble and storage characteristics of peptide sex hormones
Stored in vesicles as prohormones
Large secretory capacity
Released upon stimulus
May appear in urine in biologically active form (allows determination of pregnancy)
Examples of peptide hormones
Anterior pituitary tropic hormones
Insulin
Compare anterior and posterior pituitary
Anterior Pituitary
Adenohypophysis
Epithelial component
5 cell types- secrete 6 hormones (LH/FSH same cell type)
Posterior Pituitary
Neurohypophysis
Neural component
Release 2 neurohormones
What does FSH target
Follicle stimulating hormone
Target Ovarian follicular cells to make estrogen and progestins
Target Sertoli cells to initiate spermatogenesis
What does LH target
Luteinizing hormone
Target Leydig cells to make testosterone
What does prolactin target
Mammary glands to initiate and maintain milk production
What does oxytocin target
Uterus and breast
What type of GPCRs do GnRH and FSH/LH use
GnRH- Gq
FSH/LH- Gs
How was GnRH pulsatile secretion proven
Monkey experiment where ovaries were removed
Name corresponding hormones to their pulse frequency
Low- FSH
High- LH
Role of inhibins and activins and what type of hormone they are
Peptide hormones
Act to fine tune hormones we have discussed
Activins- enhance action of hormone
Inhibins- downregulate
What can increases in inhibin A and inhibin B cause
A- increase trisomy 21
B- decrease fertility in males
