Test 6 Endo Thyroid Slides 128-186 Flashcards
(73 cards)
1
Q
What gland has a butterfly shape and is the largest of the “pure” endocrine glands?
A
Thyroid Gland
2
Q
What is the location of the Thyroid Gland?
A
- Lateral lobes on ea. side of trachea projecting upward.
- Inferior to larynx
- Lobes connected by isthmus
- 3rd lobe: extends superior from isthmus, called pyramidal lobe (50% of people have)
3
Q
What are the functional units of the thyroid?
A
Follicle
4
Q
What is the shape of the wall of the follicle and what does it consist of?
A
Sphere shape
Consists: Follicular cells
5
Q
What is the inside of the follicle called?
A
Colloid
6
Q
What is the name of the cells that reside in between the follicular spheres and produces calcitonin and has no direct action on thyroid hormones?
A
Parafollicular Cells
7
Q
What is the inactive form of thyroid hormone and is much more abundant but less potent?
A
Tetraiodothyronine (Thyroxine, T4)
8
Q
What is the active form of thyroid hormone and is much more potent but less abundant?
A
Triiodothyronine (T3)
9
Q
What is hormone is produced by the parafollicular cells in the thyroid gland and helps regulate calcium?
A
Calcitonin
10
Q
The Thyroid is the only endocrine gland that stores its hormones in large quantities, how many days worth does it store?
A
100 days worth
11
Q
Follicular cells pull what ions from the blood stream?
A
Iodide ion
12
Q
Follicular cells produce what?
A
Thyroglobulin (TGB): (Glycoprotein-carbon chain of tyrosine)
13
Q
Where is TGB produced in the Follicular cell?
A
Endoplasmic reticulum
14
Q
Where is the TGB packaged and is released by what means into what space of the Follicular cell?
A
- Packaged: Golgi apparatus
- Released: Exocytosis into lumen (colloid)
15
Q
What oxidizes the iodide to create the useable form for thyroid hormone synthesis? What is this form?
A
Perioxidase Oxidizes Iodide (2I-) into Iodine (I2)
16
Q
The Tyrosine (on TGB) and iodine in the colloid of the Follicular cells react forming bonds, What does the reaction create?
A
- Monoiodotyrosine (MIT): One iodine to one Tyrosine
- Diiodotyrosine (DIT): Two iodines to one Tyrosine
17
Q
The MIT and DIT molecules form bonds between each other, what do they form?
A
- T3 (3 iodine molecules): MIT + DIT
- T4 (4 iodine molecules): DIT + DIT
18
Q
What stimulates TSH secretion from the Anterior Pituitary Gland?
A
TRH (Thyroid Releasing Hormone)
19
Q
What effect does increased demand for ATP have on T3/T4 production?
A
Increases production of T3/T4
- Cold Environment
- Hypoglycemia
- High Altitude
- Pregnancy
20
Q
The colloid is pulled back into the follicular cells by pinocytosis, what is contained in the colloid?
A
T3 and T4
21
Q
What occurs within the follicular cell once the colloid is inside?
A
- Lysosome engulf colloid
- Digest TGB
- Cleaves T3 and T4
22
Q
After the T3 and T4 are cleaved from the TGB what occurs to the hormone?
A
- Secreted out of the follicular cell into interstitial space and into the bloodstream
- Lipid soluble- easy diffusion
23
Q
More than 99% of T3 and T4 are bound to what so it may travel through the blood stream?
A
Thyroxine-Binding Globulin (Transport Proteins)
24
Q
What actions do the Thyroid Hormones have within the body?
A
- Increase basal metabolic rate (BMR)
- Stimulates synthesis of additional Na+/K+ pumps
- Helps regulate metabolism
- Enhance actions of catecholamines (some)
- Works w/hGH and insulin to accelerate body growth
25
What is Basal metabolic rate (BMR)?
Rate of oxygen consumption under normal conditions
| -When increased, BMR causes metabolism of carbohydrates, proteins, and lipids
26
The action of Thyroid Hormones to stimulate synthesis of additional Na+/K+ pumps results in what?
- Increased ATP production and consumption by constant turnover of Na+ and K+
- Reactions release heat as byproduct
- Heat helps raise and maintain body temperature
27
Thyroid Hormones help regulate metabolism in what ways?
- Stimulates protein synthesis
- Increases use of glucose and FA for ATP production
- Increases lipolysis and enhances cholesterol excretion
28
What catecholamines does Thyroid Hormone have an enhancing effect on?
Epinephrine and Norepinephrine
-T3 and T4 upregulate beta receptors in the presence of epi and norepi
(upregulation explains hyperthyroid patients experiencing increased heart rate and BP)
29
What systems does Thyroid Hormones, working w/ hGH and Insulin to accelerate body growth, mainly affect and deficiency of T3/T4 results in what for fetal growth?
Systems: Nervous system and Skeletal Systems
| Fetal Growth: infancy or childhood causes severe mental retardation and stunted bone growth
30
The parafollicular cells outside of the follicle cells but inside the thyroid produce what hormone?
Calcitonin
31
What function does Calcitonin have?
- Lowers blood levels of Ca2+ and HPO4^2- by inhibiting bone RESORPTION by osteoclasts
- Accelerates uptake of calcium and phosphates into bone extracellular matrix
32
What will stimulate and inhibit the secretion of Calcitonin hormone from the parafollicular cells?
Stimulate: High level of blood Ca2+
Inhibit: Low level of blood Ca2+
Blood Calcium levels directly control secretion
33
What are some etiologies (causes) of Hypothyroidism?
- Inadequate Thyroid Hormone synthesis and secretion from thyroid gland (Iodine deficiency)
- Inadequate secretion of TSH from Anterior Pituitary
34
Severe hypothyroidism may cause what? What Signs and Symptoms does this have?
Myxedema
| S/S: Edema of facial tissues, decrease in HR, cold intolerance, dry hair and skin, muscle weakness, lethargy
35
What condition arises from untreated congenital hypothyroidism in children? What is associated with it?
Cretinism
| -Stunted growth, mental retardation, impaired motor neuron dysfunction, constipation
36
What is a usual cause of congenital hypothyroidism in children?
Severe lack of iodine or immune dysfunction
37
What causes the formation of a Goiter?
- Untreated iodine deficiency
| - Thyroid overworks to keep up w/demand for T3/T4 and hypertrophies
38
What disease is an autoimmune disorder caused by production of Thyroid-Stimulating Immunoglobulin (Autoantibody) that mimics TSH at TSH receptors?
Graves' Disease (Hyperthyroidism)
39
What occurs to the Thyroid gland due to the overstimulation brought on by Graves' disease?
Hypertrophy of the gland (2-3x's larger)
| -Over-function until burnout and turns into Hypothyroid condition
40
What are some Symptoms and clinical signs of Hyperthyroidism?
```
Hyperexcitability/Anxiety
Heat Intolerance
Excessive Sweating
Weight Loss
Muscle Weakness
Extreme Fatigue w/occasional inability to sleep
Elevated heart rate
Hand Tremor
Exophthalmos
```
41
What are the four small glands partially embedded in the posterior surface of the Thyroid gland (2 per lateral lobe), weighing about 40mg, w/the functional component being principal cells (AKA Chief Cells), referred to as? What do they secrete?
Parathyroid Glands
| -Secrete parathyroid hormone (PTH)
42
Parathyroid Hormone (PTH) is the major regulator of what and has the specific function to do what?
-Regulator: Calcium, magnesium, and Phosphate levels in the blood
-Function: Increase number and activity of osteoclasts
(results in increased bone resorption--> Releases Calcium and Phosphates into blood)
43
What is the difference between Resorption and Reabsorption? Give Example for each.
-Resorption: Process of losing a substance
Ex: Breakdown of bone by osteoclasts in order to increase plasma Calcium
-Reabsorption: Process of gaining (absorbing) again
Ex: Osteoblast reabsorbing Calcium from blood to build bone matrix
44
Where else does PTH have effects and what are those effects?
Kidneys
- Slows loss of Calcium and phosphate from blood into urine
- Promotes kidney formation of Calcitriol (Active form of Vit. D) (Calcitriol (D3) increases absorption of Calcium, magnesium, Hydrogen Phosphate (HPO4^2-) in GI
45
Hypoparathyroidism results in what?
Hypocalcemia: Muscle spasms, twitches, tetany
-Convulsion
-Possible death
Increases neuronal permeability to Sodium: allows for decreased threshold
46
What is the treatment for Hypoparathyroidism?
High-dose Vitamin D (Specific time period)
| Increase dietary Calcium intake
47
Hyperparathyroidism results in what?
Hypercalcemia (Increased resorption of bone matrix):
-Decalcified, weakened, easily-fractured bone
Causes weak muscles
Increased risk of kidney stones: due to high concentration of calcium and phosphate in blood which ends of in urine
48
What causes the secretion of ACTH (Adrenocorticotropic Hormone) from the Anterior Pituitary?
Corticotropin-Releasing Hormone (CRH) form the Hypothalamus
49
ACTH (Adrenocorticotropic Hormone) effects/targets cells located where? What is released in response to ACTH?
Zona Fasciculata in the Adrenal Cortex
| -Glucocorticoids are released
50
What will Stimulate and Inhibit the release of CRH (Corticotropin Releasing Hormone)?
Stimulate: Low glucocorticoids in blood=increased CRH
Inhibit: High glucocorticoids in blood= Decreased CRH
51
Describe the anatomy of the Adrenal Glands?
-Pair of flattened, pyramidal shaped glands
-Located superior and adjacent to kidneys (retroperitoneal)
-Ea. gland has two distinct sections
(Adrenal Cortex- lg. peripherally located)
(Adrenal Medulla- smaller centrally located
-Covered by connective tissue capsule
-Highly Vascularized
52
How many layers is the Adrenal cortex divided into and what are the names for each layer?
3
Zona Glomerulosa
Zona Fasiculata
Zona Reticularis
53
Which Zona of the Adrenal Cortex is the outer zone made up of closely packed cells in spherical clusters, secretes mineralcorticoids and affects mineral homeostasis?
Zona Glomerulosa
54
95% of mineralocorticoid activity in the body is due to what?
Aldosterone
55
What does Aldosterone regulate and what does it promote?
Regulate: mineral ions Sodium and Potassium: helps regulate BP and Blood Volume
Promote: Excretion of Hydrogen ion in urine preventing acidosis
56
What controls the secretion of Aldosterone?
Renin-angiotensin-aldosterone system (RAAS)
57
Aldosterone is important in correcting what?
Dehydration
Sodium Deficiency
Hemorrhage
58
Which zone of the Adrenal Cortex is the middle zone with cells arranged in long, straight columns, Secretes glucocorticoids (mainly cortisol) and affects glucose homeostasis?
Zona Fasciculata
59
The Glucocorticoids secreted by the Zona fasciculate of the Adrenal Cortex are responsible for what?
Regulate Metabolism
| Resistance to Stress
60
Glucocorticoids are also know as what? What are the names of the Glucocorticoids?
Corticosteroids
- Cortisol (most abundant, 95% of activity)
- Cortisone
- Corticosterone
61
What are the functions of glucocorticoids?
- Protein Breakdown: mainly in muscle fibers, ATP production
- Glucose Formation: Liver converts Lactic Acid or AA to Glucose
- Lipolysis: Stimulate breakdown of Triglycerides
- Resistance to Stress
- Anti-inflammatory Effects
- Depression of Immune Response
62
The function of Resistance to stress by glucocorticoids is in response to what and how does it accomplish this?
Response to: Exercise, Fasting, Fright, Hypo/Hyperthermia, Bleeding, Infection, Surgery, Trauma, and Disease
By: Increasing blood glucose (primarily for Brain)
-Increasing BP (Hemorrhage) by increasing sensitivity of blood vessels to vasoconstrictor action
63
The function of Anti-inflammatory effects by glucocorticoids is accomplished how?
Inhibits WBC that participate in inflammatory responses
- Inhibition of WBC's- tissue repair is slowed
- Used clinically in Tx of chronic inflammatory diseases
64
What are some adverse effects of excess Glucocorticoids?
- Decreases connective tissue repair for wound healing
- Decreases resistance to infection (immunosuppression)
- Increases risk for osteopenia or osteoporosis (protein catabolism causes loss of organic bone matrix)
- May cause mental disturbances
65
Which zone of the Adrenal Cortex is the inner zone and its cells are arranged in branching cords, secretes small amounts of weak androgens?
Zona Reticularis
66
What weak androgen is secreted by the Zona Reticularis and what affects does this have on Male and Females?
Dehydroepiandrosterone (DHEA)
Male: insignificant Testos causes all androgenic effects
Female:
-Promotes Libido (Sex Drive)
-Converted into estrogen by other tissues
-After menopause only estrogen from conversion of adrenal androgens
(Minor roll in pubic and axillary hair growth in boys and girls and lends to growth spurts)
67
What is caused from increased production of ACTH from the pituitary which causes increased cortisol?
Cushing's Disease
68
What is caused from increased cortisol from the adrenal glands WITHOUT increased ACTH or ACTH secreting tumor elsewhere in the body (markedly elevated levels)
Cushing's Syndrome
69
Cushing's Disease/Syndrome both cause what?
- Breakdown of muscle proteins
- Redistribution of Body Fat
- Constant increased level of cortisol
70
Constant increased level of cortisol may results in what?
```
Hyperglycemia
Osteoporosis
Weakness
Hypertension
Increases susceptibility to infections
Mood Swings
```
71
Similar Signs and Symptoms of Cushing's Disease/Syndrome may be seen in patients treated with what for what?
Corticosteroids (Prednisone)
| For: Asthma, Post Organ Transplant, Chronic Inflammatory Diseases
72
What disease is characterized by the hyposecretion of glucocorticoids and aldosterone, caused by autoimmune diseases that attack receptors for ACTH or cause adrenal cortex destruction or by pathogens such as tuberculin bacteria, Symptoms usually don't present until 90% of cortex is destructed?
Addison's Disease
73
Addison's Disease symptoms may include what?
```
Mental Lethargy
Anorexia
Nausea and Vomiting
Weight Loss
Hypoglycemia
Muscular Weakness
Skin may have "bronzed" appearance
```
