ENDOCRINOLOGY PART 2 Flashcards
(113 cards)
1
Q
positioned in the lower anterior neck and shaped like
a butterfly. It is made up of two lobes resting on each side of the
trachea, bridged by the
A
thyroid | isthmus
2
Q
critical in regulating
metabolism and other body functions.
All are organized into
A
thyroid - follicles
3
Q
Spheres of thyrocytes or thyroid cells surrounding a viscous substance
called
A
colloid
4
Q
structural unit of thyroid cells composed of follicular cells.
A
follicle
5
Q
in the center there’s a colloid incharge of production of T3 & T4
A
follicular cells
6
Q
viscous substance is the central core of the follicle.
○ It is a fluid or liquid that is mainly a glycoprotein iodine complex also known
as
A
colloid - thyroglobulin
7
Q
Mainly composed of thyroglobulin or thyroid glycoprotein.
A
colloid
8
Q
incharge of secreting calcitonin
regulation of calcium
A
parafollicular cells
9
Q
These hormones influence nearly every organ system, impacting processes ranging
from heart rate and body temperature to digestion and energy expenditure.
A
thyroid hormone
10
Q
in the colloid. It’s the protein precursor of thyroid hormone.
○ Undergoes a process through adding iodine to become T3, T4, rT3 which are
produced only by thyroid follicular cells.
○ Rich in an amino acid called
A
thyroglobulin - tyrosine
11
Q
to regulate metabolism
A
Increased heat production
12
Q
enhances mitochondria and use of oxygen
in the process
A
Increased oxygen consumption
13
Q
upregulate; increased sensitivity to
catecholamines; influences the heartrate and metabolism
A
Increased adrenergic receptors -
14
Q
regulates (calcium levels ) electrolytes by inhibiting the bone resorption of calcium
A
calcitonin
15
Q
signals the follicular cells to ingest a microscopic droplet of colloid by
endocytosis.
A
TSH
16
Q
then secreted by the thyroid cell into the circulation.
A
T4 and T3
17
Q
tropic hormone that
acts on the thyroid gland.
A
TSH
18
Q
Precursor of T3 and T4
A
tyrosine
19
Q
with 4 iodine attached to tyrosine
It is the precursor of T3 and rT3
A
T4
20
Q
○ with 3 iodine left because of the iodination of one iodine in the outer ring. Nawala isang iodine
(iodinized).
○ Metabolically active form of metabolism therefore
functional
A
T3 - outer, active
21
Q
when inner iodine is lost, still 3 iodine.
An inactive metabolite of T4, which can also
compete with the receptors of T3, but it is inactive,
therefore it gives no help
A
rT3
22
Q
Thyroid hormone synthesis is dependent on iodine because it is primarily made of trace element iodine.
A
TRUE
23
Q
Can be found in seafood, dairy products, iodine-rich bread, and vitamins.
A
iodine
24
Q
Recommended minimum daily intake of iodine:
A
150 ug
25
The enzyme needed and responsible for adding iodine to the tyrosine (iodination
of tyrosine).
Conjugation of iodine to form T3 & T4.
thyroid peroxidase
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produced from the rough endoplasmic reticulum of the follicular cell. It leaves the cell via exocytosis to enter the colloid
______ is rich in tyrosine, which are the rings you see in the structure
thyroglobulin
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Iodination of thyroglobulin will form
Monoiodothyronine (MIT) and
Diiodothyronine (DIT)
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Conjugation of 1 DIT and 1 MIT residue forms
triiodothyronine
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conjugation of 2 DIT
tetraiodothyronine
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is done by THYROID PEROXIDASE
conjugation
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Principal secretory product
Prehormone for T3 production
tetraiodothyronine
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If the question is what is the prohormone, the answer is ______ because it is
the source of tyrosine for the production of our thyroid hormones
thyroglobulin
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T4
3,5,3,5 tetraiodothyronine
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T3
3,3’,5 triiodothyronine
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Metabolically active thyroid hormone
Major product of the tissue deiodination of T4
triiodothyronine
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responsible for the deiodination of T4
to form T3 or rT3
monodeiodinase
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If it removes an iodine in the inner ring of T4, it is now
rT3 (3,3,5 triiodothyronine)
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Most abundant is
T4
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undergo deiodination to form T2
rT3 - 3,3’triiodothyronine
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a. Found in liver and kidney
b. Most abundant
TYPE 1 iodothyronine 5- deiodinase
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a. Found in brain and pituitary gland
b. Maintain constant levels of T3 in the CNS
TYPE 2 idiodothyronine 5- deiodinase
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These are carrier molecules in the bloodstream that transport thyroid hormones,
ensuring their stability and distribution throughout the body. They play a crucial
role in regulating the availability of thyroid hormones to target tissues by controlling
their circulation and release
MAJOR BASIC PROTEIN
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most significant MBP
TBG thyronine binding globulin
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MBPS
TBG thyroxine binding globulin
TBPA thyroxine binding pre albumin
ALBUMIN
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condition characterized by excessive production of thyroid
hormones, typically resulting from an overactive thyroid gland. Symptoms may
include weight loss, rapid heart rate, anxiety, tremors, and heat intolerance.
Problem is directly on the thyroid gland
Symptoms include pale to yellow skin, dry skin, exophthalmos
HYPERTHYROIDISM
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Thyroid-stimulating hormone ↓
Triiodothyronine (T3)↑
Tetraiodothyronine (T4)↑
primary hyperthyroidsim
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Thyroid-stimulating hormone ↑
Triiodothyronine (T3)↑
Tetraiodothyronine (T4)↑
secondary hyperthyroidsim
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drug used to treat arrythmias
○ This drug blocks to conversion of T4 to T3
amiodarone
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also causes an acute inhibition of thyroid hormone production
Wolff-Chaikoff Effect
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most common
In women
■ With TPO antibodies
■ Thyroid hormone levels revert to normal after several months
■ 4 years after postpartum, there is still persistent hypothyroidism
■ Have goiter
postpartum thyroiditis
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painful thyroiditis:
subacute granulomatous thyroiditis,
subacute nonsuppurative thyroiditis, or
de Quervain’s thyroiditis
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characterized by neck pain, low-grade fever, myalgia, a tender diffuse goiter, and swings in thyroid
function tests
■ No TPO antibodies
■ Elevated thyroglobulin levels
subacute granulomatous thyroiditis,
subacute nonsuppurative thyroiditis, or
de Quervain’s thyroiditis
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only 5% to 9% of thyroid nodules prove to be thyroid cancer
thyroid nodules
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small, pea-sized glands
located near or attached to the thyroid gland in the
neck. They secrete parathyroid hormone (PTH),
which plays a crucial role in regulating calcium levels
in the blood and maintaining proper bone health.
parathyroid gland
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Affects the bone, kidneys, and GI tract for calcium
homeostasis
Smallest of the endocrine system
parathyroid gland
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Form the majority of the cells in the parathyroid
They are small cells around 5-8 um in diameter with
very dark nuclei and with a very very thin cytoplasm
These are the secretor that secretes the parathyroid
hormone
chief cells
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Larger and with dark nuclei and the cytoplasm is
strongly eosinophilic because of the numerous
mitochondria present in the cells
Non-secretory
Appear after the first decade of life
oxyphil cells
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Involved gland: parathyroid gland
calcium homeostasis
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Range of ionized calcium is
1.24 umol/L
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Levels of calcium or the ionized calcium itself is the determinant if there is a
problem with the hormones affecting them which is the PTH and relatively your
vitamin D = not a hormone
activated vitamin D= calcitrol
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If there is low calcium we stimulate the PTH and it increases bone resorption,
prevents urinary loss, and 1,25 Vit D production to increase GI absoprtion
TRUE
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If calcium is high calcium will go back to the bones, can urinate na and stops the
production of 1,25 Vit D
TRUE
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part of the kidney where calcium is reabsorbed
distal convoluted tubule
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condition marked by intermittent muscular spasms so this is caused by
a malfunction in the parathyroid gland causing a deficiency in calcium
TETANY
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electrolyte that is also needed in the physiological function of
the muscles so without it it causes tetany
calcium
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abnormally high PTH because we cannot absorb vit
D and calcium therefore low levels of calcium and will cause high PTH
malabsorption syndrome
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no absorption of calcium in GI tract also no trigger to stop
PTH, so PTH is increased
vitamin d deficiency
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○ detects biologically active PTH by its ability to induce formation of cAMP
○ Low calcium levels the parathyroid gland releases more PTH
CAP assay: cAMP inducible PTH
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This type of PTH activates another enzyme which
adenylate cyclase
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can also be estimated in needle biopsy specimens obtained from parathyroid
tumors.
PTH
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leads to tetany and altered neuromuscular
activity (Chvostek’s sign and Trousseau’s sign)
Calcium level < 8 mg/dL (2.0 mmol/L)
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twitching of the face/ facial muscles
Chvostek’s sign
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when a pressure is applied to the arm (ex. cuff of
sphygmomanometer) there is twitching or spasm in the arm
Trousseau’s sign spasm
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laryngeal stridor
■ Collapse of larynx
○ seizures: tonic-clonic, focal motor, atypical absence and akinetic seizures
Calcium level < 6 mg/dL (1.5 mmol/L)
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Stimulating or suppressing a particular hormonal axis, and observing the appropriate hormonal response
DYNAMIC FUNCTION TEST
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If excess is suspected: conduct a
suppression test
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If deficiency is suspected: conduct a
stimulation test
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Patient Preparation: complete rest 30 minutes before
blood collection
Best specimen: fasting serum
Screening Test: Physical Activity/Exercise test
Confirmatory Test : Insulin Tolerance Test (Gold
Standard)
DIAGNOSTIC TESTS FOR
GH INSUFFICIENCY
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insulin is administered to produce hypoglycemic
stress
<2.2 mmol/L
80
Under diagnostic tests for GH insufficiency
Done when hypopituitarism is suspected
also known as Insulin Tolerance Test
insulin stress test
81
DIAGNOSTIC TESTS FOR
ACROMEGALY THAT SCREENING TESTS
Somatomedin C or Insulin-like growth factor 1
(IGF-1)
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Confirmatory Test of DIAGNOSTIC TESTS FOR
ACROMEGALY
Glucose Suppression Test/OGTT
83
provide a 75 grams of oral glucose then
monitor the level of growth hormone
OGTT
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should suppress GH to <1ug/ L
hyperglycemia
85
Failure to suppress GH below 2 ug/L can
actually indicate the presence of acromegaly
and it is also associated with higher
prevalence of diabetes mellitus, heart diseases
and hypertension because OGTT is also used
as a confirmatory test for diabetes mellitus
below 2 ug/L
86
A.k.a. Concentration Test or Dehydration Test (Gold
standard) or indirect water deprivation test
Patient Preparation: No fluid intake for 8-12 hours
(Ideal should start: 10:00 PM
○ Or until 5% of the fluid has been lost
○ Avoid smoking and caffeine intake that might
affect AVP output
overnight water deprivation test
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to continue to
excrete dilute urine; UOsm < 300 mOsm/kg
Central or nephrogenic DI <300 mOsm/kg
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to concentrate urine; UOsm
300-800 mOsm/kg
prinary polydipsia 300-800 mOsm/kg
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if the serum Osm increases to >
305 mOsm/kg, it is highly suggestive of
DI
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Reference range Serum Osmolality:
275-295
mOsm/kg
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Reference range Urine Osmolality (UOsm):
300-900 mOsm/kg
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is a sign of DI
>295 mOsm/kg
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Screening test for adrenal insufficiencies
Differentiates the types of adrenal insufficiencies
cosyntropin
tetracosactide test
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injection of TRH and measurement of the output of
TSH
Provide synthetic TRH
TRH is involved in the hypothalamic-pituitary-thyroid
axis
used in the diagnosis of combined pituitary-thyroid
disorders
Differentiates secondary hypothyroidism and
tertiary hypothyroidism
TRH is given as an IV bolus
Blood sampling done at 0, 20, and 60 minutes
THYROTROPIN
RELEASING HORMONE
(TRH) STIMULATION TEST
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Confirms borderline response to ACTH stimulation
test
Confirmatory test for Secondary Adrenal
Insufficiency - gold standard test
INSULIN TOLERANCE TEST
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Patient prep: fasting (8 hours)
Oral dose: 0.05 U/kg of insulin
Requirement: induced hypoglycemia
INSULIN TOLERANCE TEST
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Ideal serum glucose: <40 mg/dL (after insulin dose)
Blood collection: 0, 15, 30, 45, 60, 90, and 120 mins
following oral insulin
INSULIN TOLERANCE
TEST
98
Assesses hypogonadism
Can be done together with anterior pituitary function
test (IST, TRH, GnRH tests)
GNRH TEST
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GnRH causes marked rise in LH
(increments of greater than or equal to 15 U/L)
and smaller rise in FSH (> 2 U/L)
adults
100
GnRH causes a marked rise in FSH
and smaller rise in LH
children
101
used for the diagnosis of MTC (Medullary
Carcinoma of the Thyroid)
Also used to assess the result of thyroidectomy
Can also be used to detect residual C-cells
a malignancy of the calcitonin-secreting cells of the,thyroid gland
commonly associated with an elevated calcitonin
level, but an elevated level may not always be
obvious.
Pg dose IV: 0.5 ug/kg body weight
pentagastrin stimulation test
102
sensitive indicator of
endogenous coritsol
URINE FREE CORTISOL
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Best time of collection: 6 am to 8 am (avoid drinking
alcohol before and during the urine collection)
24-hour urine collection (follow usual diet & drink
fluids as you ordinarily would)
cortisol testing
104
Screening test: plasma aldosterone
concentration/plasma renin activity ratio (PAC/PRA)
Confirmatory test: saline suppression, oral sodium
loading, fludrocortisone suppression, and captopril
challenge test
Saline Suppression Test
Dose:2 L NaCl
Procedure: dose should be infused in 2 hours
hyperaldosteronism test
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Primary hyperaldosteronism: > 10 ng/dL plasma
aldosterone
TRUE NORMAL < 5ng/dL
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autoimmune disorder where the immune system mistakenly attacks the
thyroid gland, leading to inflammation and eventual destruction of thyroid tissue. This
can result in hypothyroidism, causing symptoms such as fatigue, weight gain, and
depression.
HASHIMOTO’s THYROIDITIS
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Also known as Chronic Lymphocytic Thyroiditis
Most common cause of hypothyroidism
Targets thyroid gland
Thyroid gland increases in size
Associated with goiter
TPO antibody is positive
HASHIMOTO’s THYROIDITIS
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111
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causes hyperthyroidism due to the production of autoantibodies
called thyroid -stimulating Immunoglobulins (TSIs). These antibodies mimic the
action of thyroid-stimulating hormone (TSH) and bind to the receptors on thyroid
follicular cells.
Most common cause of thyrotoxicosis
graves’ disease
113
