Endocrine Physiology and Pathology Flashcards
What is the endocrine system?
What is an important job of the endocrine system?
Acts with the nervous system and coordinates all the activity of tissues and organs, but is slower than the nervous system.
To main homeostasis!
What is the number one function of the endocrine system?
Hormones- amines, steroids etc. are all secreted by glands in the body via the endocrine system and transported via blood
What all does the endocrine system control?
Reproduction
Control of blood pressure
Maintenance of electrolyte, water, and nutrient balance of blood
Regulation of cellular metabolism and energy balance
Responses of cardiac cells
Growth and development
Homeostasis
What is the difference between endocrine and exocrine hormones?
What are examples of both systems?
Exocrine glands act directly and are nonhormonal substances (sweat, saliva, GI secretions) they also have ducts to carry secretion to membrane surface
Endocrine glands produce hormones and lack ducts
What are the different types of hormones?
Autocrine- Chemicals that exert effects on same cells that secrete them
Paracrine- Locally acting chemicals that affect cells other than those that secrete them
Local Chemical Messengers
What are positive and negative feedback mechanisms with relation to regulation of hormonal concentration?
What are some salient factors that determine the response of the target tissues to hormones?
What are the names of common endocrine hormones and which gland secretes them?
What are the endocrine glands?
Pituitary
Thyroid
Parathyroid
Adrenal
Pancreas
Pineal Gland
What is the main organ that links the nervous system and the endocrine system?
Hypothalamus is the neuroendocrine organ
Are glands exclusively exocrine or endocrine?
What is an example?
NO, some glands can have both endocrine and exocrine functions
Pancreas- secrete insulin and glucagon
What other tissue/ organs produce hormones?
Adipose cells
Thymus
Cells in walls of small intestine
Stomach
Kidney
Heart
What is the main gland of the endocrine system?
Pituitary Gland
What is a hormone?
Long distance chemical signals that travel in lymph and blood
What are the 3 major classes of endocrine hormones? What does each class do?
- Amines- Release into blood
- Peptide hormones- Stored in secretory vesicles in the gland after synthesis and released into blood
- Steroids- not stored in secretory vesicles and released into blood
What do hormones as as?
What are the mechanisms of hormone action?
Hormones act as receptors depending on their chemical nature and receptor location
- Water soluble hormones
- Lipid Soluble hormones
What is the base of water soluble hormones? What is the exception?
What do they act on ?
What can water soluble hormones not do?
Amino acid based hormones except thyroid hormone.
Water soluble act on:
- Plasma membrane receptors
- Act via G protein second messengers
They cannot enter the cell
What is the base of lipid soluble hormones?
What do they act on ?
What can lipid soluble hormones do?
Steroid and thyroid hormones
Act on intracellular receptors that directly activate genes
They can enter the cell because they are hydrophobic and lipid soluble
What is the water soluble pathway?
Is it quick or slow?
Quick pathway- works in seconds
- Hormone (1st messenger) binds receptor
- Receptor activates G protein (Gs)
- G protein activates adenylate cyclase
- Adenylate cyclase converts ATP to cAMP (2nd messenger)
- cAMP activates protein kinases
- Reponses of target cell (activates enzymes, stimulates cellular secretion, opens ion channel, etc.)
What are the other signaling pathways?
Hormone binding stimulates phospholipase C which produces IP3 and calcium is released
What is the lipid soluble hormone pathway?
How quick is the pathway?
Pathway is slow and works in hours because of transcription and translation
- The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor
- The receptor hormone complex enters the nucleus
- The receptor hormone complex binds a specific DNA region
- Binding initiates transcription of the gene to mRNA
- The mRNA directs protein synthesis
How is blood concentration of circulating hormones controlled?
Which is most common?
Feedback control mechanisms
- Negative Feedback control
- Positive feed back control
Negative feedback is the most common
What does negative feedback control do?
Which type of control does this mechanism produce?
What is an example?
Successful physiological action results in inhibition of hormonal release
Negative feedback loops are stabilizing
IE: Regulation of thyroid hormone
What does positive feedback control do?
Which type of control does this mechanism produce?
What is an example?
Successful physiological action results in further increase in hormonal release
Positive feedback loops are destabilizing
IE: Hormonal control of development of the ovarian follicle and ovulation
What are the other factors affecting target cell responses?
What does each response do?
Can multiple hormones act on the same target at the same time?
- Permissiveness
- One hormone cant exert its effects without another hormone being present - Synergism
- More than one hormone produces same effects on target cell - Antagonism
- One or more hormones opposes action of another hormone
YES!
What is an example of permissiveness?
Thyroid hormone with reproductive hormones
What is an example of synergism?
Follicle stimulating hormone and Luteinizing hormone on ovulation -> amplification
What is an example of antagonism?
Insulin and glucagon glycogen storage
- Insulin promotes while glucagon antagonizes
What are 7 endocrine gland examples?
Hypothalamus
Anterior Pituitary
Posterior Pituitary
Thyroid Gland
Parathyroid Gland
Endocrine Pancreas
Adrenal Medulla
What are the hormones associated with the hypothalamus, ant. pituitary, post. pituitary, thyroid gland, parathyroid gland, endocrine pancreas, adrenal medulla
What are the steps of the hypothalamic- pituitary axis?
What is the hypothalamic- pituitary target endocrine organ feedback loop?
- Hypothalamus releases a hormone
- Hypothalamic hormones stimulate release of pituitary hormones
- Pituitary hormones stimulate targets to secrete more hormones
Hormones from final target organs inhibit release of anterior pituitary hormones
What does the hypothalamus release? What is its target organ?
Thyrotropin releasing hormone is released and acts on the anterior pituitary
What does the anterior pituitary release? What is its target organ?
Thyroid- stimulating hormone (Thyrotropin) acts on the thyroid gland
What does the thyroid gland release?
What is its target organ?
What is the target mechanism?
Thyroid hormones acts on target cells by stimulating or inhibiting the target cells
What does feedback control mechanism do?
Which type of control does it exert?
What are the names of the feedback control mechanisms?
It ensures that circulating hormonal levels are matched to physiological needs.
Exerts direct or indirect control of endocrine organ
Negative feedback control
Positive feedback control
What is the most common feedback control mechanism?
What is its role?
When is it present?
What is an example?
Negative feedback
Successful physiological action which results in inhibition of hormonal release- it is stabilizing
It is always present and it very common
Regulation of thyroid hormone
What is the rare feedback control mechanism?
What is its role?
When is it present?
What is an example?
Positive feedback
Successful physiological action results in further increase in hormonal release- it is destabilizing
It is not very present and is rare in the endocrine system
IE: Hormonal control of development ofo the ovarian follicle and ovulation
What is an example of positive feedback in the ovaries?
When does this occur in the mensuration cycle?
Estrogen and progesterone have positive feed back on the pituitary gland and hypothalamus. Estrogen causes the hypothalamus to secrete more GnRH which makes the pituitary gland secrete more LH/FSH -> Acts on ovaries to secrete more Estrogen/ Progesterone.
Day 12-14 (ovulation)
What is an example of negative feedback in the ovaries?
Can negative feedback be overwritten?
How often does this occur?
Estrogen and progesterone have negative feed back on the pituitary gland and hypothalamus. Estrogen causes the hypothalamus to stop secreting more GnRH which makes the pituitary gland NOT secrete more LH/FSH .
This mechanism is overwritten by positive feedback until LH/FSH reach their maximum.
Occurs through out most the cycle?
What occurs with low levels of T3/T4?
Which type of feedback loop is implemented?
Low levels of T3/T4 (low metabolic rate/ decreased body temp) -> stimulate the hypothalamus to release TRH -> stimulates the pituitary gland -> release TSH -> stimulates thyroid to release T3/T4 -> too much T3/T4 -> INHIBITS hypothalamus and pituitary galnd
Which factors affect target cell response?
- Presence of receptors
- Hormone concentrations influence the number of receptors
What are examples of receptors affecting the target cell response?
Which receptors are present all over the body?
ACTH receptors are found on certain cells of the adrenal cortex thus only certain cells respond to ACTH
Thyroxin receptors are found on nearly all cells of the body
What happens in up regulation and down regulation of hormone concentrations?
What is an example of each?
In up regulation target cells form more receptors in response to low hormone levels
- Chronic decrease
In down regulation target cells lose receptors in response to high hormone levels
- Chronic increase
ie: Diabetes, epinephrine, Tolerance
What is the relationship between the hypothalamus and pituitary gland?
How are they connected?
What are the endocrine functions of the hypothalamus?
What starts at the hypothalamus?
The hypothalamus and pituitary function as a unit to regulate the function of other endocrine glands
Connected via the infundibulum
Regulates releasing hormones and inhibiting hormones from the anterior pituitary gland
Posterior pituitary hormone synthesis starts here
How many ways does the hypothalamus control release of hormones from the pituitary gland?
What are the steps of the first pathway?
2 ways- neuronal connection/ vascular connection
- When stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus
- Hypothalamic hormones travel through portal veins to the ant. pituitary where they stimulate or inhibit release of hormones made in the anterior pituitary
- After the releasing hormones, the anterior pituitary secretes hormones into the secondary capillary plexus -> empties into the general circulation
How do the hypothalamus and pituitary gland communicate?
What is the system called?
Communicate via vascular connections:
- Superior hypophyseal artery to hypothalamic capillary bed to a portal vessel to anterior pituitary capillary bed to hypophyseal vein
Hypothalamus- Hypophyseal portal system
What are the hormones secreted by the anterior pituitary gland?
- Growth Hormone
- Prolactin
- Thyroid Stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- Follicle stimulating hormone (FSH)
- Lutenizing Hormone (LH)
What is growth hormone also known as?
Which cells release GH?
What is the % released?
Somatotropin or somatotrophic hormone
Secretory cells- Somatrotropes (ant. pituitary cells that produce growth hormone)
20%
What is the pathway of the neuronal connection?
Where does this process begin?
What begins in the hypothalamus and what ends in the posterior pituitary?
- Hypothalamic neurons synthesize oxytocin or ADH
- Oxytocin and ADH are transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary
- Oxytocin and ADH are stored in axon terminals in the post. pituitary
- When hypothalamic neurons fire, AP arriving at the axon terminals cause oxytocin or ADH to be released into the blood
Starts @ paraventricular nucleus
Supraoptic and paraventricular nuclei in hypothalamus and axonal endings in the posterior pituitary
What are the hormones released from the posterior pituitary?
What are the functions of these released hormones?
Antidiuretic Hormone (ADH) aka Vassopresin
- Regulation of body fluid osmolarity
- Vascular smooth muscle contraction
Oxytocin
- Milk ejection
-Uterine contraction
Which type of hormone in growth hormone?
What GH also known as?
Which type of pattern is seen with GH secretion? How often is it secreted? When is the largest amount of secretion occur?
How does the secretion of GH change? What are the changes seen at certain stages of life?
Peptide Hormone
Somatotropin or somatotropic hormone
Diurnal pattern- Pulsatile secretion occurs ever 2 hours with the largest secretion at night
GH changes over lifetime:
1. Increases from from birth to early childhood and stabilizes
2. Secretory burst during puberty (induced by estrogen & testosterone)
3. Secretion declines from puberty to adulthood and stabilizes
4. Secretion reduces during senescence
What are the factors that increase GH secretion?
- Reduced glucose and free fatty acid concentration increase GH
- Starvation increases GH
- Exercise increases GH
- Stress, fever, trauma, anesthesia increase GH
- Puberty increases GH
- a- adrenergic agonists increases H
What are the factors that decrease GH secretion?
- b-adrenergic agonists decrease GH
- Somatostatin and somatomedin decrease GH
What is the ending for growth hormones that increase?
- Tropin & Trophic
What is the ending for growth hormones that decrease?
- Statin and Medin
What are the 4 mechanisms of inhibition for growth hormone?
- Hypothalamus secrete Somatostatin (SRIF) which inhibits the Ant. pituitary
- Somatomedin directly acts on the Ant. pituitary and blocks GH secretion
- Somatomedin acts on the hypothalamus which secretes SRIF (somatostatin) to inhibit the ant. pituitary from secretion GH
- Growth hormone releasing hormone (GHRH) inhibits the hypothalamus from releasing more GHRH
Which hormones block the anterior pituitary?
Somatostatin (SRIF)
Somatomedins (IGF)
Which hormones block the hypothalamus?
Somatomedins (IGF)
Growth Hormone Releasing Hormone (GHRH)
What are the direct effects of GH?
- Increases blood levels of fatty acids for fuel; protein synthesis
- Glycogen breakdown and glucose release to blood (anti-insulin effect)
- Decreases rate of glucose uptake and metabolism- conserving glucose
Direct and powerful actions on metabolism
What are the indirect effects of GH?
What are they mediated through?
Mediated through somatomedins
- Increases metabolism of cartilage and bone to promote linear growth
- Increases protein synthesis
What are the direct actions of GH?
What are the direct actions also known as?
- Fat metabolism
- Carbohydrate metabolism
Metabolic and anti-insulin
What does carbohydrate metabolism do?
Increase blood glucose and other anti-insulin effects
What does fat metabolism do?
Increased fat breakdown and release
What are the indirect actions of growth hormone?
- Skeletal
- Extraskeletal
- Secretion of Insulin-like growth factors (IGF)
What are the skeletal effeccts?
Increased cartilage formation and skeletal growth
What are the extraskeletal effects?
Increased protein synthesis, and cell growth and proliferation
What occurs from excessive GH secretion before puberty?
What happens if not treated?
Gigantism
- excessive growth of long bones of arms and legs
- Tall stature
- Acromegaly
What occurs from excessive GH secretion after puberty?
Acromegaly
- Increased periosteal bone growth
- Broadening of face/jaw
- Enlargement of hands and feet
What are the effects of GH on soft tissue?
Coarse facial features
Enlargement of nose
Enlargement of visceral organs
Left ventricular hypertrophy and left heart failure
What is the common factor that leads to excessive GH?
Pituitary adenomas involving somatotropes
What are the pathophysiology causes of GH deficiency?
Causes:
- Decreased secretion of GHRH
- Reduced GH secretion
- Failure to generate somatomedins
- Deficiency of receptors for GH or somatomedins
What are the clinical consequences of GH deficiency as a child?
- Short Stature
- Prominent forehead
- Underdeveloped nose bridge
- Mild obesity
- Delayed puberty
What are the clinical consequences of GH deficiency as an adult?
- Reduced bone density
- Tendency for more bone fracture
- Higher level of body fat
- Fatigue
- Anxiety and depression
Which type of hormone is prolactin?
What is prolactin secreted by?
Peptide hormone
Hypothalamus
What is the stimulatory pathway of prolactin?
Where does it start?
Starts in the hypothalamus
Hypothalamus releases TRH which stimulates the AP to secrete prolocatin
What is the inhibitory pathway of prolactin?
Where does it start?
Starts in the hypothalamus with dopamine (prolactin inhibiting factor- PIF) promoting dopamine secretion which reduces prolactin secretion
What are the inhibitory factors of estogren?
Dopamine
What are the inhibitory factors of breast feeding?
Bromocriptine (dopamine agonist)
What are the actions of prolactin?
- Breast Development
- Lactogenesis
What are the actions of prolactin in breast development in puberty and during pregnancy?
Prolactin actions are in conjunction with estrogen and progesterone
During pregnancy there is ductal development and proliferation of alveolar epithelial cells (with estrogen)
Where is estrogen stored during puberty?
Where is progesterone stored during puberty?
-During puberty there is proliferation of mammary ducts (with estrogen) and lobules (with progesterone)
What does a deficiency in prolactin result from?
What are the symptoms?
Deficiency results from Lactotrope destruction
Symptoms are failure to lactate
What does an excess in prolactin cause? What are the symptoms?
What is the treatment?
Excess causes destruction of inhibitory pathways from hypothalamus -> prolactinoma
Symptoms: Galactorrhea, Infertility
Treatment: Dopamine analogues (bromocriptine)- Inhibits prolactin release
What occurs with lactogenesis in early pregnancy?
During pregnancy?
After pregnancy?
Early pregnancy: Casein protein production
During: Progesterone and HPL inhibit prolactin’s complete effects on lactogenesis
After: Lipids and lactose production are promoted
When does complete lactogenesis occur?
What are the 2 mechanisms that ensue?
Complete lactogenesis occurs after parturition (after giving birth)
- Progesterone and HPL levels drops
- Suckling stimulus reduces dopamine and increases encephalin
What does prolactin inhibit?
What is the mechanism in which prolactin is inhibited?
Ovulation
Gonadotrophin- releasing hormone (GnRH) synthesis in hypothalamus is inhibited
What is a prolactinoma?
What happens to males if they have a prolactinoma?
A noncancerous tumor of the pituitary gland
Males will be infertile if they have time
