Endocrinology Flashcards
What does the endocrine system consist of?
Organs or tissues that synthesize and secrete hormones
Hormones
Carrier proteins
Organs or tissues that are affected by hormones
List some organs or tissues in the endocrine system
Pituitary Hypothalamus Adrenal gland Heart Pancreas Thymus
What is a hormone?
A hormone is a chemical substance made by an organ or tissue and secreted into the blood to have a specific effect on a tissue or structure
Where is a hormone secreted into after being synthesized by an organ or tissue?
Into the blood
What are endocrine hormones?
Hormones that affect or act on distant tissue, cells or organs
What are paracrine hormones?
Paracrine hormones are hormones that act locally, that is, tissues, cells or organs close by
What are autocrine hormones?
These hormones affect the cells that synthesize them by interacting with sepecific membrane receptors on its surface to induce effects
Give an example of an endocrine hormone
Insulin
Thyroxine
Cortisol
Give an example of a paracrine hormone
Neurotransmitter
Give an example of an autocrine
Bombesin
How are hormones classified?
By their tissue of origin and by their structures
Give the four classes of hormones
Polypeptides/protein
Steroids
Amino acid derivatives
Fatty acid derivatives
Majority of hormones fall under what class?
Polypeptides/proteins
What class of hormone is soluble on water only ?
Polypeptides/proteins
Polypeptide hormones are water soluble. What does this imply?
They circulate freely. That is, unbound without transporters
What is the half-life of a polypeptide hormone?
Short half life of 10-30 minutes
What is the half-life of a steroid?
Long half life of 30-90 mins
Polypeptides/proteins are water soluble, so move freely, unbound then bind to a membrane receptor. What does this imply about their effect?
They need a second messenger to actually carry their action in the cell
Give some examples of polypeptides
Insulin
Parathyroid hormone PTH
ACTH
What hormone class is insoluble in water?
Steroids
Steroid are water insoluble. What does this imply for their movement?
They require transporters/carrier proteins
How do steroids effect their function in terms of receptors?
Since they have transporters, they do not bind to membrane but diffuse into the cell and bind to cytoplasmic receptor
Give examples of steroids
Estrogen
Cortisol
What hormone type is soluble both in water lipids?
Amino acid derivatives
These hormones can move unbound or bound.
Amino acid derivatives
These hormones are derived direct,y from amino acids
Amino acid derivatives
GIve examples of amino acid derivatives
Thyroxine
Catacholamine
These hormones are derived from fatty acids
Fatty acid derivatives
Give an example of a fatty acid derivative
Prostaglandins
List the functions of hormones
Growth and development
Homeostatic control
Regulation of energy production
Hormones function to affect growth and development in a mechanism called?
Morphogenesis
List so,e hormones that participate in the body’s growth and development
Gonadal steroids Growth hormone GH Cortisol ACTH Thyroxine TSH
How do hormones control homeostasis?
By keeping the body functioning normally via control of physiological processes
List some hormones that control digestion/utilization of sugar
Insulin
Glucagon
Incretins
List some hormones that regulate calcium levels
PTH
Vitamin D
List some hormones that regulate salt and water balance of the body
Renin
ADH
Aldosterone
List some hormones that regulate fats and proteins
Cortisol
Klein
Thyroid hormones
How do hormones regulate energy production?
By controlling storage and usage of e energy like insulin that decreases plasma glucose while glucagon/epinephrine increase plasma glucose
We also need hormones for more energy
Why is hormone transportation important?
Because it affects hormone concentration and availability in the body.
Protein hormones are transported
Unbound
Give examples of steroid hormone transporters
Albumin
Sex hormone-binding protein
Cortisol-binding globulin
Give examples of amino acid hormone transporters
Albumin
Thyroxine-binding globulin
How does liver failure affect hormone levels?
Liver failure causes a decrease in carrier proteins like albumin which are synthesized in the liver. This causes high free hormone levels
For hormones carry out biological functions directly?
No, they’re just messengers
How do hormones work?
They carry messages to the cells and the cells carry out the intended biological function
What initiated biological response of the cells?
The binding of the hormones
How do hormones bind to a cell?
By binding to a receptor Either extracellularly (on surface) or intracellularly (inside the cell in cytoplasm or on nuclear membrane)
What the two characteristics import to hormone receptors?
High specificity
High affinity
Which hormones bind to receptors on cell surface?
Proteins
How do proteins bind cell surface membrane receptors?
By exerting control over phosphorylation of these functional molecules. They induce a conformational change in the receptor which leads to a cascade of signs, events.
The binding of polypeptides to cell surface receptors allow them to exert control over the phosphorylation of these functional molecules creating a conformational change in the receptors leading to a cascade of signal events. What are these events?
Activation of G proteins (secondary messengers)
Formation of cAMP
What are G proteins?
Secondary messengers needed by protein hormone binding on cell surface
This is a very important messenger get for the signal transduction pathway induced by protein hormones.
cAMP
What does the formation of cAMP result to?
Activation of protein kinases
What is the role of protein kinases?
Protein kinases carry out the biological functions causing phosphorylationon of other substances increasing their activity
This substance is considered the first messenger in either an activating or inhibitory response.
Hormone
Give the order of events in protein cell surface binding
Protein binding to cell surface receptor
G protein coupled receptor binds protein hormone
G protein subunits begin a cascade of enzyme activation
cAMP generation
Activation if protein kinases
Biological function
How do steroids and thyroid hormones bind into the cell?
By diffusing passively into the cell then binding to intracellular receptors
How does hormone intracellular binding work?
Hormone-receptor complex makes a conformational change and migrates into nucleus then binds to DNA. It directly controls DNA expressions at a specific gene and either activated gene transcription or repress gene transcription
Where is the hypothalamus located?
At the base of the brain directly above the pituitary gland
How is the hypothalamus connected to the pituitary gland?
By nerves and blood vessels called the pituitary stalk
This organ is the highest command center of the endocrine system
Hypothalamus
What are neurons in the hypothalamus responsible for?
Synthesizing releasing factors and inhibiting facts that regulate pituitary function
What is the basic organization of the endocrine system?
Hypothalamic pituitary axis
The pituitary gland is under the control of the
Hypothalamus
How does the hypothalamus control the pituitary gland?
By secreting releasing hormones to regulate pituitary activity
In a case, the hypothalamus secretes thyrotropin releasing hormone (TRH) which stimulates the pituitary to secrete thyrotropin/TSH which in turns stimu,ages the thyroid gland to secrete thyroid hormone. What is this called?
Positive regulatory function
What two things regulate pituitary function
Hypothalamus
Negative feedback mechanism
In a case, thyroid hormone inhibits the pituitary gland and reduces secretion of TSH. What is this called?
Negative feedback mechanism
What is another name for the pituitary gland?
Hypophysis meaning under the hypothalamus
Where is the pituitary gland located?
In the bone cavity at the base of the brain
Name the two parts of the pituitary gland
Anterior pituitary (adenohypophysis) Posterior pituitary (neurohypophysis)
Why is the pituitary gland called the ductless gland?
Because is secreted hormones directly into the blood
Hormones are synthesized in how many different cell types a.
Five 5
Secretion of hormones is controlled by?
Hypothalamus releasing factors
Negative feedback loops
List all the hormones made by the anterior/adenohypophysis pituitary gland
Growth hormone GH Adrenocorticotropic hormone ACTH Prolactin PRL Thyroid stimulating hormone TSH Lutenizing hormone LH Follicle stimulating hormone FSH
List the hormones made in the posterior/neurohypophysis pituitary gland
ADH
Oxytocin
ACTH is released in response to
CRH (Corticotropic releasing hormone)
What does ACTH do?
Stimulates the adrenal cortex as stress response
Thai is stressed due to her IR exams on Friday morning. What hormone is going to be released by her pituitary gland?
ACTH
After being stimulated by ACTH, the adrenal gland releases corticosteroids. What types of corticosteroids are released by the adrenals. Give examples.
Glucocorticoids- cortisol, corticosterone
Mineralocorticoids- aldosterone
Androgens
What is the main stress hormone?
Cortisol
What does cortisol do?
It increases circulating glucose, suppresses the immune system and inflammation
What is the function of aldosterone?
Regulation of water, BP and heart rate
ACTH is regulated by
Circadian rhythm
When are cortisol levels highest and lowest?
Highest in the morning and lowest at night
When is growth hormone released?
After onset of sleep
What inductee the anterior pituitary gland to secrete GH?
Growth hormone releasing factor from the hypothalamus
Growth hormone is inhibited by ?
Somatostatin
What is creases growth hormone in the body?
Sleep Exercise Stress Hypoglycemia (low glucose) Other hormones
List the functions of growth hormone
Promotes growth in soft tissue, cartilage and bone
Stimulates protein synthesis
Mobilizes fat (lipolysis)
Releases IGF-1
This hormone promotes growth in soft tissues, bones, cartilage
Growth factor
This polypeptide effects most of the growth hormone’s actions
Insulin-like growth factors (IGF-1)
Secretion of growth hormone is described as
Episodic and pulsatile
Why is one time measurement of growth hormone inconclusive?
Because it is released in the body in episode and pulses
One time measurement of what correlates better with grown hormone related clinical conditions?
IGF-1
Prolactin is low in these two individuals
Males
Non pregnant females
What is the main function of prolactin?
Initiation and maintenance of lactation during and after pregnancy
How does prolactin initiate and maintain lactation during and after pregnancy?
Induces breast tissue growth
Synthesizescertain milk proteins
What are the other functions of prolactin aside initiation and maintenance of lactation?
Immune system function
Induces synthesis of steroid hormones in ovaries
What is the primary control of prolactin levels?
PRL inhibiting factor
What is the inhibitor of prolactin?
Dopamine
Dopamine (prolactin inhibiting factor) is affected by the presence of
Oxytocin, progesterone, estrogen, thyroid hormones and insulin in circulating blood
LH and FSH fall under what category?
Gonadotropins
Gonadotropins are important in what?
Reproductive function of both males and females
What does luteinizing hormone do?
Induces synthesis and secretion of sex hormones like estrogen and testosterone
What does follicle secreting hormone does?
Promotes germ cell production for ovulation and spermatogenesis
Hypothalamic neurons send what to the posterior pituitary gland?
Their axons
Where are neurohypophysis hormones made and stored?
Made in the hypothalamus. Stored in the neurohypophysis
What is the only proven clinical function of oxytocin?
Stimulating contraction of the uterus during labor for birth
Oxytocin is primed by
Estrogen
What are the two sex hormones synthesized and secreted by the luteinizing hormone?
Estrogen and testosterone
What is another function of oxytocin that indicates it works with prolactin?
Milk let down reflex function. Stimulating lactating mammary gland for breastfeeding
What is a another name for ADH?
Vasopressin
What are the two main functions of ADH?
- Maintain water balance by regulating the kidney to reduce urine production and resort water in renal tubules
- Vasoconstriction: Increasing BP by contracting muscle wall of capillaries and arterioles
Typically, how many hormones are affected in hyperpituitarism?
One hormone made by one cell type
What is primary hyperpituitarism?
This is hyperpituitarism in which the problem is intrinsic to the pituitary gland like pituitary adenoma (tumor) or hyperplasia (hyperproliferating normal cells)
What is secondary hyperpituitarism?
This is hyperpituitarism in which the problem comes from either overstimulation of the hypothalamus or ectopic production of a hormone occurring by a non endocrine tissue like a tumor
Hypo secretion of hormones can involve one, several or all hormones. Hyposecretion of all hormone is called
Panhypopituitarism
Sing,e hormone hypopituitarism usual,g results from what?
The destruction of one specific type of cells in the pituitary
What is the most common cause of hypo pituitarism?
Pituitary adenoma
How does a functional tumors affect pituitary secretion?
A functional tumor usually results in hyper secretion of the one hormone made by that tumor causing hypo secretion of all others
How does a non functional tumors affect pituitary secretion?
A non functional tumor leads to tissue destruction and hypo secretion of all hormones
Effects of hyoersecretion of growth hormone are
Age dependent
How does hypersecretion of growth hormone manifests in children?
Gigantism. Proportional enlargement of all portions of the body.
How does hypersecretion of growth hormone manifests in adults?
Acromegaly. Progressive enlargement of distal extremities like hands, feet and face, soft tissues
List the symptoms seen in hypersecretion of growth hormone
- Excessive growth and soft tissue problems including vasculature issues
- Hyperglycemia with possibility of developing DM
- Large facial features, overgrown tongue, enlarged heart
- Death in case of cardiac failure, respiratory failure or neurological issues
What are the symptoms of hypo secretion of growth hormone?
Stunted growth in adolescence. Dwarfism in children
Hypoglycemia
Adult GH deficiency
What is the most common form of dwarfism?
Achondroplasia
How does hyposecretion of growth hormone affects glucose and insulin?
Decreased growth hormone decreases gluconeogenesis and increases tissue insulin sensitivity
What are the symptoms seen in adultGH deficiency?
Low muscle mass and bone density
High fat mass and adverse lipid profile
Cardiovascular risk
Low energy, irritability
How is hyposecretion of GH treated?
GH injection therapy
Vasoritide
What is laron syndrome?
A rare autosomal recessive genetic form of dwarfism in which tissue is resistant to growth hormone
How is laron syndrome different from achondroplasia?
In Laron syndrome, there is enough growth hormone in the body but lack of growth hormone receptors on tissues causing no synthesis of IGF so growth issues but achondroplasia is actual,y lack of growth hormone
What is the most common hypothalamic/pituitary disorder?
Hyperprolactinemia
Hyperprolactinemia leads to?
Galactorrhea (inappropriate milk production)
Amenorrhea in females (cessation of periods)
Infertility in males
What causes Hyperprolactinemia?
Stress, sleep loss, low sexual stimulation, certain drugs, decreased dopamine
Pituitary adenoma, hypothyroidsm, liver or renal failure
Hypogonadism
What is the name given to hypersecretion of ADH?
Syndrome of inappropriate ADH - SIADH
What is the name given to hypo secretion of ADH?
Diabetes insipidus
What causes SIADH?
Sustained production/release of ADH, ectopic tumors, lung cancer
Kidney preserves too much water
Urine output greatly reduced/concentrated/hypertonic
How is sodium affected in SIADH?
Dilutional hyponatremia cuz of low Na levels from excess water rentention
What symptoms are seen in SIADH?
Weakness
Poor mental function
Coma (brain edema)
What are the two types of diabetes insipidus seen in hyposecretion of ADH?
Primary - hypothalamus under secretes ADH
Secondary- kidney is not sensitive to ADH
What are the symptoms of hyposecretion of ADH?
Fluid loss
Polydipsia
Polyuria
Altered mental status
What do labs show in diabetes insipidus?
Normal glucose Very concentrated blood Hypernatremia High protein levels Diluted urine
How do nerve cells differ in SIADH and DI?
Nerve cells swell in SIADH and shrink in DI
What is pitocin?
Synthetic IV dose of oxytocin given to some women during labor if their uterus doesn’t seem to be contracting long or strong enough to advance their labor or birth
