Final Exam: Thyroid + Parathyroid Glands Flashcards
viscous protein rich liquid that is the main form of thyroid hormones, found in the follicular cells
colloid
Cell located outside the follicles that secretes calcitonin
C cell
what is the function of calcitonin
calcium metabolism
What two molecules are important for thyroid hormone synthesis
tyrosine and iodine
where is tyrosine derived from?
thyroglobulin
Where is thyroglobulin formed?
within the folicle cell and secreted into the colloid
where do we get iodide from?
iodine from the diet is converted to iodide in the intestine and transport to the thyroid
is concentration of iodide greater intra or extracellular?
inracellular
What is the first step in thyroid hormone synthesis?
oxidation of iodide to iodine
what enzyme helps in the oxidationof iodide to iodine
thyroid peroxidase (TPO)
what is organification of the thyroglobulin?
binding of iodine with the thyroglobulin molecule
Tyrosyl ring can accomodate __ iodine molecules
2
when 1 molecule attaches to the tyrosyl ring
monoiodotyrosine (MIT)
When 2 molecules attach to the tyrosyl ring
diiodotyrosine (DIT)
1DIT + 1DIT=
Thyroxine (T4)
1MIT + 1DIT=
Triiodothyronine (T3)
What are the 2 types of T3
- Triiodothryronine
2. reverse T3
when is reverse T3 produced?
during disease states in peripheral tissues
The main drug used to treat hyperthyroidism is an inhibitor of _______
TPO
___ is the major hormone produced by follicular cells
T4
where does most of the body T3 come from
Peripheral deiodination of T4 on target tissues
thyroid hormones will be secreted after stimulation by ____ produced in the adenohypophysis
TSH
Where is TRH released from?
hypothalamus
How are thyroid hormones transported to target tissue?
in plasma attached to proteins (Thyroxine binding globulin and albumin)
Thyroid hormones are the primary factors for the contorol of _____.
Metabolism
What are the 4 actions of thyroid hormones?
- inc the number of mitochondria and activity of mitochondria
- inc. the basal metabolic rate of cells
- stimulate carbohydrate metabolism
- fat metabolism
- growth and development
- inc. blood flow and cardiac output
- inc. HR
- GI effects
What are some C/S of hypothyroidism?
- lethargy
- weight gain
- skin problems
- myxedema
- ocular problems
- badicardia
- hyperlipidemia
What are some C/S of hyperthyroidism?
- polyphagia
- wt. loss
- hyperactivity
- V+
- D+
- PU/PD
- Alopecia
- Tachycardia
Main organ involved in the calcium and phosphate metabolism
Parathyroid gland
What are the 2 functions of phosphate in physiological homeostasis?
- participate as chemical buffer
2. make up the composition of cell membrane and intracellular components
Where is most of the body’s phosphate stored?
bones
What are some roles of calcium?
- Muscle contraction
- N. cell activity
- Release of hormones by exocytosis
- Coagulation
- Activation of enzymes
- Maintenance of membrane stability
- Structural integrity of bones and teeth
Where is a majority of calcium stored in the body?
bones
What are the 3 diff ways calcium can be found in the blood?
- bound to proteins (40%)
- Combined with anions (10%)
- Ionized (50%)
What is the biologically active form of calcium?
Ionized Ca
The regulation of calcium levels involves control of the movement of calcium between the ECF and what 3 organs?
- Bones
- GI tract
- Kidneys
What 3 hormones are involved in the reagulation of calcium?
- PTH
- Vit. D
- Calcitonin
WHere is PTH produced?
Chief Cells in the parathyroid
What are the two types of cells in the parathyroid gland?
- chief cells
2. oxyphil cells
What 2 hormones are produced in chief cells
PTH and Parathormone
Which cells in the parathyroid are sensitive to a dec. in iCa
chief
What type of receptors are located in chief cells?
Calcium sensing receptors
Gprotein coupled receptors
What activated the calcium sensing receptors in chief cells?
dec. in iCa
The effect of PTH is to inc/dec calcium and inc/dec phosphate concentrations in ECF
inc. Ca
dec. Phosphate
PTH has a direct effect on ____ and ____ metabolism of Ca
bone and kidney
PTH has an indirect effect on ____ metabolism of Ca
GI tract
PTH binds to receptors on osteocytes and stimulates ______.
osteocytic-osteolysis
PTH bindson osteoblast cells and stimulates ______
production of osteoclast-activating factor which stimulates osteoclasts
PTH acts on the distal convoluted tubules in the kidney causeing ____
inc. absorption of Ca
How does PTH affect the distal convoluted tubules?
dec. renal phosphate absorption
Which Vit. does PTH activate in the kidney
Vit D
_____ stimulates the actie transport of dietary calcium across the intestinal epithelium
Calcitriol
PTH secretion is mainly controlled by ___
iCa
What is iCa?
free (ionized) Ca conc. in the blood
A Dec. in iCa will cause a inc/dec in PTH
inc.
Where is calcitonin produced?
C Cell (parafollicular cell) of the thyroid
What hormone acts to counter balance PTH?
calcitonin
What regulates the secretion of calcitonin
Calcium and GI hormones
What are the 4 actions of Calcitonin?
- dec. movement of Ca in bone
- Dec bone reabsorption
- Inc. movement of phosphate from ECF into bone
- Inc renal excretion of Ca
Inc Ca:
hypercalcemia
Dec. in Ca
hypocalemia