Chapter 7- The Endocrine Glands Flashcards
What is the thyroid gland?
Two lobes of endocrine tissue joined in missile by narrow portion of gland
What are the functional unit of the Thyroid?
Follicular cells (follicle)
How are follicular cells arranged in the thyroid gland?
Into hollow spheres which form a follicle
What is the lumen of follicular cells filled with?
Coloid
What is the function of coloid in follicular cells?
Serves as extracellular storage for thyroid hormone
What kind of hormones does the thyroid produce?
Two iodine-containing hormones derived from amino acid tyrosine
What are the 2 hormones that the thyroid produces?
Tetraiodothyronine (T4 or thyroxine)
Triiodothyronine (T3)
What neuroendocrine cells does the thyroid have?
C cells
What do C cells secrete?
Peptide hormone called Calcitonin
What is the thyroid gland responsible for?
Synthesis, storage and secretion of thyroid hormone
What are the 2 basic ingredients of thyroid hormone?
- tyrosine (synthesised by body)
- Iodine (dietary intake)
Where does synthesis of TH occur?
On thyroglobulin molecules with colloid
How does tyrosine enter the colloid?
Tyrosine-containing thyroglobulin is exposed from follicular cells into colloid via exocytosis
How does the iodine enter the colloid?
via Iodine pump after thyroid captures iodine in the blood
What happens to tyrosine and iodine in the colloid?
Iodine attaches to tyrosine and forms thyroid hormones
How does thyroid store thyroid hormone?
Remind in colloid
-Until split off and secreted
-Enough is stored to supply body for several months
How are thyroid hormones secreted?
Follicular cells phagocytise thyrogolbin-laden colloid which frees T3 and T4 to diffuse into blood
What kind of hormones is thyroid hormone?
Amine
-has 2 tyrosines
-Has iodine
What is the chemical nature of thyroid hormone?
Lipophilic
-Transported by plasma protein
What percent of each thyroid hormone is produced?
T4 - 90%
T3 - 10%
Why is T3 produced less than T4?
because T3 is four times more potent than T4
Where are the target cells that cleave iodine to form T4?
Mainly in the liver and kidney
What plasma protein does T4 bind with?
Thyroxine-binding globulin
Where are receptors for thyroid hormones found?
Nuclei of most of the cells in the body
-allows for widespread action
What are thyroid hormone major actions?
- basal Metabolic rate and heat production
- Sympathomimetic (permissive action)
- Growth and CNS development
How does thyroid hormone determine basal metabolic rate?
-Stimulates Na/K ATPase
-Generates heat during glycolysis
-Calorigenic action
What is thyroid hormoneâs sympathomimetic effect?
Increases target-cell responsiveness to catecholmines
How does thyroid hormone have a sympathomimetic effect?
Permissive action
Increases HR and force of contraction
-Increase b-adenorecptors on heart
How does thyroid hormone effect nervous system development?
Hormones help develop the nervous system properly
-lack of hormone can affect growth
What happens if there is an absence of T3 and T4 during fetal life?
Congenital hypothyroidism
(cretinism)
What is the effect of Congenital hypothyroidism?
poorly developed NS and severely compromised intellectual function
What can cause Congenital hypothyroidism ?
Lack of iodine in pregnant mother
How is thyroid hormone essential for normal growth?
Stimulates Gh release and IGF-1 production
Enhances effects of GH and IGF-1 on target cells
What is the function of TSH?
Regulates steps in thyroid hormone synthesis and release
What happens if there is an absence of TSH?
Thyroid gland atrophy
What happens if there is an excess of TSH?
Thyroid gland hypertrophy and hyperplasia causing a Goiter
What regulates thyroid gland secretion?
A negative-feedback system
-Hypothalmic TRH
-Anterior pituitary TSH
-Thyroid gland T3 and T4
What are two main categories of abnormalities of the thyroid gland?
- Hypothyroidism
- Hyperthyroidism
What is th term often used for Hypothyroidism in adults?
Myxedema
What does Myxedema cause?
Mucopolysaccharides accumulate under the skin forming an edna
What are the symptoms of Hypothyroidism??
Increased sensitivity to cold -calorigenic
Weightgaincâcalorigenic
Easily fatigued
Slow weak pulse âcardiac
Impaired mental function
How is Hypothyroidism treated?
-replacement hormone therapy
-Dietary iodine
What may occur with hypothyroidism?
Goiters
(Too much TSH)
How are goiters treated?
-Exogenous thyroid hormone
-Dietary iodine if its a deficiency causing it
What is the most common cause of hyperthyroidism ?
Graveâs disease
(autoimmune disease)
What is Graveâs disease?
Body incorrectly produces thyroid-stimulating immonoglobulines which act like TSH
What is a prominent characteristic of those with Graveâs disease?
Exophthalmos
-Protruding eyes
What are symptoms of hyperthyroidism?
Heat intolerance
Weight loss including skeletal muscle
Increased appetite
Increased SNS activity: anxiety, tremors, increased HR
How is hyperthyroidism treated?
-Surgical removal of portion of the over-secreting thyroid
-radioactive iodine
-Antithyroid drugs
What are adrenal glands?
Glands embedded above each kidney in a capsule of fat
What are the two exocrine organs composing the Adrenal glands?
- Adrenal cortex
- Adrenal medulla
What is the adrenal cortex?
Outer portion
What doe the adrenal cortex secrete?
Steroid hormones
What does the adrenal medulla secrete?
catecholamines
(epinephrine and NE)
What are the 3 zones/layers of the adrenal cortex? (outmode to innermost)
Zona golerulosa
Zona fasciculata
Zona reticularis
What does the Zona glomerulosa secrete?
Aldosterone
(outermost layer)
What does the Zona fasciculata secrete?
Main source of Cortisol
DHEA
(middle layer)
What does the Zona reticularis secrete?
DHEA
some cortisol
(innermost layer)
What is the largest portion/layer of the adrenal cortex?
Zona fasciculata
What are the 3 categories of adrenal steroids?
- Mineralocorticoids
- Glucocorticocoids
- Sex hormones
What are Mineralocorticoids?
Influence mineral balance (Na and K)
Mainly aldosterone
What are glucocorticoids?
Major role in glucose metabolism and protein and lipid matabolism
Mainly cortisol
What are sex hormones?
Identical or similar to those produced by the gonads
-Most important is DHEA
What is DHEA?
dehydroepiandosterone
(male âsexâ hormone)
What are all adrenal cortex hormones based from?
All cholesterol-based
What is the chemical nature of cholesterol-based hormones?
Hyrophopic
Carried by plasma proteins in blood
What plasma protein is Cortisol bound to?
Corticosteroid-binding globulin (transcortin)
What plasma protein is aldosterone and DHEA bound to?
Albumin
what is aldosteroneâs principal action site?
Distal and collecting tubules of the kidney
What increases aldosterone secretion?
Renin-angiotensin-aldosterone system
How is the RAS triggered?
When blood sodium levels drop or potassium levels rise Renin is released by the adrenal glands
What s aldosteroneâs function?
Help kidneyâs retain sodium and excrete potassium
What part of the brain does aldosterone act independently of?
The anterior pituitary
What are 2 main disorders of adrenocortical function?
- Aldosterone hypersecretion
- Adrenoctical insufficiency
What can cause aldosterone hyper secretion?
-Hypersecreting adrenal tumour made of adolsterone-secreting cells
-Inapropriately high activity of RAS
What does a hypersecreting aldosterone tumour cause?
Primary hyperaldosteronism aka Connâs syndrome
What does inappropriately high activity of the RAS cause?
Secondary hyperaldosteronism
what are symptoms of Aldosterone hyper secretion?
-Excessive Na retention and K depletion
-HIGH blood pressure
What causes Primary adrenocortical insufficiency?
Addisonâs disease
Autoimmune disease (most common)
Loss of cortical region
-Leads to aldosterone and cortisol deficiencies
What does an aldosterone deficiency cause?
-Hyperkalemia and hyponatremia, hypotension
What does a cortisol deficiency cause?
Poor response to stress
Hypoglycemia
Lack of permissive action for many metabolic activities
Why does secondary adrenocortical insufficiency occur?
Occurs because of pituitary or hypothalamic abnormality
What hormone does secondary adrenocortical insufficiency cause a deficiency of?
ONLY CORTISOL
-No hypothalamic hormones to trigger the release of it
What is the most abundant Glucocorticoid? aka Corticosteroids
Cortisol
What does cortisol stimulate?
-Hepatic gluconeogenesis
-Protein degradation in tissue especially muscle
What is Hepatic gluconeogenesis
the process where the liver makes new glucose molecules from non-carbohydrate sources
e.g; amino acids
What does Cortisol inhibit?
Glucose uptake and use by many tissues (not the brain tho)
-Increases plasma glucose
What does cortisol facilitate?
Lipolysis
-Fatty acid increases in blood
What emotion does cortisol play a key role in adapting to?
Stress
What is cortisol secretion regulated by?
negative-feedback loop involving CRG and pituitary ACTH
Cortisol displays a charecteristic _______ _______
Dinural Rhythm
-Cortisol levels are highest in the morning and lowest at night
Cortisol is a permissive action hormone, what hormones requires its presence?
Permits catecholamines, epinephrine
What does epinephrine require cortisol for?
To induce vasoconstriction to prevent circulatory shock in stressful situations
What is the same for Cortisol hyper secretion?
Cushingâs syndrome
What causes Cushingâs syndrome?
- Overstimulation of adrenal cortex by excessive amounts of CRH and ACTH (Cushingâs disease -most common)
2, Adrenal tumours that secrete cortisol independent of ACTH
- ACTH-secreting tumours located in places other than the pituitary
What does Cushingâs syndrome cause?
Hyperglycemia -diabetes mellitus levels
Redistribution of fat
Muscle weakness
Osteoperosis
Immunosuppression
Hypertension
Hypercortisolism stratia
Thin legs and arms, fat on trunk and face
Red cheeks
How is fat redistributed in Cushingâs syndrome patients?
Buffalo hump
Moon face
What causes Hypercortisolism-stratia in Cushingâs syndrome patients?
Protein breaks down in skin
-Stretch mark-like appearance
How is Cushingâs syndrome treated?
Depends on the cause:
-Surgial removal of pituitary tumour
-Adrenalectomy
What sexes does the adrenal cortex produce sex hormone in?
Both
What is the name of the adrenal sex hormone with biological importance?
DHEA
Dehyroepiandrosterone
In males what happens when DHEA is secreted?
It is overpowered by testicular testosterone
In females when DHEA is secreted?
-Causes pubic and axillary hair growth
-Enhances pubertal growth spurt
-Develops and maintains female sex drive
What hypothalamic hormone controls DHEA?
ACTH
-not gonadotropins FSH and LH
What is the name for Adrenal androgen hyper secretion?
Adrenogenital syndrome
What are symptoms of Adrenogenital syndrome in Adult females?
Hirsutism (male like body hair)
Deepening of voice
More muscular arms and legs
Smaller breasts
Menstruation ceases
What can cause Adrenogenital syndrome?
Cortisol insufficiency
-because it increases ACTH, which stimulates DHEA
What does DHEA inhibit?
Gonadotropins
-during hyper secretion of DHEA can lead to sterility
How is Adrenogenital syndrome treated?
Glucocorticoid therapy
What are the symptoms of Adrenogenital syndrome in newborn females?
Have male-type external genitalia
What are symptoms of Adrenogenital syndrome in Prepubertal males?
precocious pseudopuberty
What are symptoms of adrenogenital syndrome in Adult males?
No apparent effect
What nervous system is the adrenal medulla a modified part of?
The sympathetic nervous system
What is the primary stimulus of the adrenal medulla?
Stress
What hormones does the adrenal medulla release?
Catecholamines
How much of each catecholamine does the adrenal medulla release?
Epinephrine 80%
Norepinephrine 20%
Why do the actives of adrenal medulla catecholamine vary?
Their activities depend on different adrenergic receptor types
-alpha and beta adrenoceptors
What are the functions of Epinephrine?
aka Adrenlaline
-reinforces SNS (systemic response to fight or flight)
-Maintains arterial BP
-increases blood glucose and blood fatty acids
How does epinephrine increase blood glucose and blood fatty acids?
-Stimulates Gbuconeogensis in the liver
-Stimulates glycogenolysis in the liver and skeletal muscles
-Inhibits insulin secretion
-increase glucagon secretion
What is a stress response?
Pattern of reactions to a situation that threatens homeostasis
What is stress?
nonspecific response of body to any factor that overwhelms the bodyâs ability to maintain homeostasis
What is a stressor?
Any harmful stimulant that brings about the stress response
Examples of stressors?
Physical â hot/cold, trauma
Chemical â reduced O2
Physiological â exercise, pain â Infections - bacterial
Emotional â anxiety, sorrow
Social â lifestyle changes
What is the stress responses actions coordinated by?
Hypothalamus
What does a generalised stress response activate?
SNS
CRH-ACTH-cortisol system
Why does a stress response activate the SNS?
Prepare body for fight-or flight response
-Epinephrine
Why does a stress response activate the CRH-ACTH-cortisol system?
Helps body cope by mobilizing metabolic resources
What does a genralized stress response cause?
Elevation of blood glucose and fatty acids
Maintaince of blood volume and blood pressure
How is blood glucose and fatty acids elevated during a stress response?
Insulin decreases
Glucagon increases
What is metabolism?
All the chemical reactions that occur within the cells of the body
What is intermediary/fuel metabolism?
Includes reactions involving the degradation, synthesis, and transformation of proteins, carbohydrates, and fats
What is anabolism?
buildup or synthesis of larger organic macromolecules from small organic subunits
â â â â â-> â
What do anabolism reactions require?
ATP energy
What do anabolism reactions result in?
- Manufacture of materials needed by the cell
2.Storage of excess ingested nutrients not immediately needed for energy
What is Catabolism?
breakdown or degradation of large, energy-rich organic molecules within cells
â â-> â â â â
What are the two levels of catabolism breakdown?
- Hydrolysis of large molecules into smaller subunits
- Oxidation of smaller subunits to yield energy for ATP production
What hormones are most important in regulation fuel metabolism?
Insulin and glucagon
What are the endocrine cells of the pancreas called?
Islets of Langerhans
What are the 4 specific islet cells in the endocrine pancreas?
- ÎČ (beta) cells
- α (alpha) cells
- ÎŽ (delta) cells
- PP cells
What do ÎČ (beta) cells do?
Site of insulin synthesis and secretion
What do α (alpha) cells do?
Produce glucagon
What do ÎŽ (delta) cells do?
Pancreatic site of somatostatin synthesis
What are PP cells?
Least common islet cell
Secretre pancreatic polypeptide
What kind of hormone is Insulin?
Anabolic hormone
When does the secretion of insulin increase?
During absorptive state
What is a major stimulus of insulin secretion?
Blood glucose concentration
What does insulin promote the cellular uptake of?
-Glucose
-Fatty acids
-Amino acids
*lowers blood concentration of them
What does insulin covert glucose to?
Glycogen
What does insulin convert fatty acids to?
Tryglycerides
What does insulin convert amino acids to?
Proteins
What is the most common endocrine disorder ?
diabetes mellitus
What is a prominent feature of diabetes mellitus?
Elevated blood glucose levels
Glucose in urine
What are the 2 major types of diabetes mellitus?
Type I
Type II
What percentage of people with diabetes mellitus have each type?
10% have Type I
90% have Type II
What is Type I diabetes?
Lack of insulin secretion
What is Type II diabetes?
Normal or increased insulin secretion
-Insulinâs target cells are less sensitive
What is a classic sign of diabetes mellitus?
Polyuria
-Large urine volume produced
Why does diabetes mellitus cause polyuria?
Extra glucose exceeds capacity of nephron to absorb it
â With glucose, stays water=osmotic diuresis, causing âsweet urineâ
