THYROID GLAND CCHM Flashcards
Primarily made up of two lobes resting on each side of the trachea and are bridged together with isthmus
↑ This isthmus is tied the two lobes with the tissue of it running anterior to the trachea
↑ Posteriorly located to the trachea is the parathyroid gland
THYROID GLAND
in humans start to develop in the fetus at about 4th to 8th week of gestation
↑ Upon reaching the 11th week, that would be the time its capable of secreting its hormones
* Located in front of the lower anterior neck
* Bow tie or butterfly like (also a bowtie structure)
- * secretes ___, ___ and ___
Thyroid glands
- T3 and T4 and calcitonin
structural units of thyroid
-Each of it has a core which is made up of a ___
Follicles
- colloid
homogenous viscous fluid consisting mainly of a glycoprotein iodine complex called
___
Colloid
- thyroglobulin
is made up of an amino acid
which is tyrosine, so together, this compound binds with the iodine and is the one responsible
for the production of thyroid hormones (T3, T4,
and calcitonin)
Thyroglobulin
Follicular cells are responsible for the production and
synthesis of 2 major thyroid hormones__and __
(T3 & T4)
control the rate at which cells burn fuels from food for energy
➢ CNS activity and brain development
➢ Cardiovascular stimulation, bone and tissue growth and development
➢ GI regulation and sexual maturation
fOLLICULAR CELLS
T3 (triiodothyronine) and T4 (thyroxine)
➢ is the hormone responsible for the regulation of calcium
➢ Helps in lowering the Ca+ concentration in the blood
circulation whenever it detects that the individual has hypercalcemia
➢ Helps in promoting bone absorption of calcium
pARAFOLLICULAR CELLS (C-CELLS)
Calcitonin
Majority of the ___ are bound to protein as its carrier protein
↑ Majority are bound to ___
which primarily carries about 60% of the __ present in the blood circulation
↑ Some of the T4 is bound to ___ specifically the ___
↑ The least concentration is those that are bound to ___ molecule
thyroid hormones
thyroxine-binding globulin
T4
prealbumin
thyroxine-binding prealbumin
albumin
In terms of percentage, majority are bound and only about less than 0.2 of __ are found in its free form
T3 (free thyroxine FT4 and free triiodothyronine FT3)
___ AND __ are responsible
for the regulation of the release of T3 and T4
- These work together thru the ____
Hypothalamus and Pituitary glands
- hypothalamic pituitary thyroid axis
The hypothalamus, specifically the supraoptic and the supraventricular nuclei of the hypothalamus would be responsible for the release of the
___ which would in turn direct the pituitary gland in the production of of it
thyrotropin releasing hormone (TRH) or thyroid stimulating
hormone TSH
For tissue growth
↑ Important for metabolism
* For development of the CNS
* Elevated heat production
↑ Regulates body temperature
* Control of oxygen consumption
* It influences carbohydrate and protein metabolism
* For energy conservation
THYROID HORMONES FUNCTION
Considered as the active form of the thyroid hormone
↑ It is about 3-8 times more metabolically active as compared to T4
↑ Majority of it in the circulation is primarily a product of deiodination of T4 which typically happens in the __ or ___
* Also known as the ___
* It has the most active thyroid hormonal activity.
* Almost 75-80% is produced from the tissue deiodination of T4
TRIIODOTHYRONINE (T3)
- liver or in the kidney
-3,5,5’ triiodothyronine
Principal application:
* In diagnosing ____
* Better indicator of recovery from hyperthyroidism (as well as recurrence)
T3 thyrotoxicosis
More commonly called as the ___
* ____
* Principal secretory product of the thyroid gland
* The major fraction of organic iodine in the circulation
* A pre-hormone for T3 production
- The only source is the__
* Elevated level causes inhibition of TSH secretion, and vice versa
-Low levels on the other hand promotes the excretion of TSH by the pituitary gland or specifically
the feedback loop thru hypothalamic pituitary and thyroid axis
TETRAIODOTHYRONINE (T4)
- thyroxine
- 3,5,3’5’ tetraiodothyronine
- thyroid gland
is the most important element in the biosynthesis of thyroid hormones
-ideal amount___ (below can cause deficiency)
iodine
- 50ug/day
Iodination of tyrosine residues in the thyroglobulin results in formation of ___ and ___
monoiodotyrosine (MIT) and
diiodotyrosine (DIT)
Product of T3
One monoiodothyronine + one
diiodothyronine
4
Two diiodothyronine molecules
▪___ converts T4 into T3
Deiodination
Latent Period around 12hrs
T3
Latent Period around 72hrs
T4
Biological
Half-life OF T3
around 2 days
Biological
Half-life of t4
around 7-9 days
refers to the time it takes for the hormone to lose half of its physiological activity
Half-life
is where the effect of the activity of
hormone can be seen to a particular tissue of organ.
Latent period
Increase____
* Increase __,__ AND____
* Potentiate actions of the ____
* Interaction with other Endocrine systems
* Effect on the CNS
* Increase vitamin A and retinal synthesis
* Helps in heat generation thru ___
ACTION OF T3 & T4
- basal metabolic rate (BMR)
- Protein, Carbohydrate and Fat metabolism
- Catecholamines (adrenaline and epinephrine)
- thyronamines
complete absence
Agenesis
from base of tongue to
trachea
- The position of the thyroid is wrong
Incomplete descent
– complete failure to descend
from base of tongue
Lingual thyroid
– segment of duct persists
and presents as lump years later
Thyroglossal cyst
- Refers to an excess of circulating thyroid hormone
- Most patients are slim & thin (due to calorie burning)
- Increase appetite and decrease weight
- Presence of exophthalmia (eyes protruded)
- Heat intolerance
- Increase activity
Tachycardia
HYPERTHYROIDISM
▪ Applied to a group of syndromes caused by high levels of free thyroid hormones in the circulation.
- Pertaining to constellation of findings in which thyroid gland becomes overactive in such a way
that it produces too much thyroxine
↑ Peripheral tissues are presented with and they respond to excess of the thyroid hormone
POSSIBLE REASONS:
▪ Excess in thyroid hormone ingestion
▪ Leakage from the thyroid follicles
▪ Excessive production of the thyroid gland
THYROTOXICOSIS
TSH level is low despite the high level of thyroxine in which primarily due to the excessive circulating thyroxine or thyroid hormone telling the brain to stop or suppress further production, therefore causing the TSH to be low.
Plummer’s disease
Mood swings
▪ Restless
▪ Sleep difficulties
▪ Tremor of hands
▪ Palpitations
▪ Sore eyes (trouble focusing, irritation and
sensitivity)
▪ Goiter
▪ Heat intolerance and would perspire a lot
▪ Weight loss
THYROTOXICOSIS
(muscle hypertrophy in the
eyes)
Exophthalmos
(the non-pitting swelling
that occurs on the shins)
Pretibial myxedema
Hyperthyroidism with peculiar edema behind the eyes called exophthalmos which causes the
eye to protrude
- Hypersecretion of ____
-has a strong familial disposition which means it may be seen
among families
➢ Autoimmune disease
↑ the body is creating antibodies that activate the Thyroid Stimulating Hormone Receptor
(TSHR)
➢ Whole gland is smoothly enlarged and the whole gland is overactive
➢ Occurs 6x more commonly in women than in men
➢ TSH receptor antibodies
GRAVE’S DISEASE
=thyroid stimulating immunoglobulins (TSIs)
are the antibodies which cause the
activation of the TSHR
thyroid stimulating immunoglobulins (TSIs)
➢ The thyroid turns into a woody or stony- hard mass
↑ Under the microscope, thyroid gland tissues are seen undergone fibrosis
RIEDEL’S THYROIDITIS (RIEDEL’S STRUMA)
Known as the painful thyroiditis
↑ Viral infections might be responsible for triggering
this condition
Associated with
▪ Neck pain
▪ Low grade fever
▪ Swing in thyroid function tests.
↑ Patient would also experience myalgia (feeling of muscle pain)
↑ Tender diffuse goiter
↑ Swings in the different thyroid function test
➢ Thyroid peroxidase antibodies are absent
➢ In the laboratory, ESR and thyroglobulin levels are elevated
SUBACUTE GRANULOMATOUS/ SUBACUTE
NONSUPPURATIVE THYROIDITIS
(DE QUERVAIN’S THYROIDITIS)
- Develops whenever insufficient amounts of thyroid hormone are available to tissues
- Patients are obese in nature
- Decrease appetite; Increase in body weight
- Edematous; Increase cholesterol level
- Cold intolerance
- Decrease activity
- Bradycardia – decrease in the heart rate
HYPOTHYROIDISM
a is a primary type of hypothyroidism
(primary thyroid failure causing decline in the production of the thyroid hormones by the thyroid
glands)
➢ Caused by autoimmune damage to the thyroid, or surgical removal
➢ Underactive thyroid gland
➢ Describes the peculiar nonpitting swelling (edema) of the skin
➢ The skin becomes infiltrated by
___
➢ Primary thyroid failure -> decline in thyroxine secretion by thyroid gland
MYXEDEMA
- mucopolysaccharides
Decrease Basal Metabolic Rate (BMR)
▪ Deepening voice
▪ Depression and tiredness
▪ Cold intolerance “Puffy face”
▪ Anemia
▪ Weight gain
▪ Slow speech
▪ Dry & yellow skin
-Caused by hypercarotenemia
(increase beta carotene in the blood circulation)
▪ Constipation
▪ Bradycardia (Heartrate < 60bpm)
▪ Eventual myxedema coma
HYPOTHYROIDISM
Also known as the ____
➢ The most common cause of primary hypothyroidism
➢ Described by ___
➢ An autoimmune disease in which thyroid gland is attacked by variety of antibody mediated immune response
↑ The possible antibody seen in patients is the ___ or
they may also have __ antibodies
➢ The thyroid is replaced by a nest of lymphoid tissue
➢ Associated with enlargement of the thyroid gland (goiter)
➢ Acquired hypothyroidism in later childhood due to development of autoantibodies to thyroid tissue
components
HASHIMOTO’S DISEASE
(CHRONIC AUTOIMMUNE THYROIDITIS)
- chronic lymphocytic
thyroiditis
- Hashimoto in 1912
-thyroid peroxidase antibodies (TPO Ab)
- thyroglobulin
A congenital condition of severely stunted physical and mental growth due to untreated congenital deficiency of thyroid hormones (congenital hypothyroidism) due to maternal
nutritional deficiency of iodine
Physical and mental retardation to newborns
➢ hyposecretion of thyroid hormones during fetal life or infancy
➢ Iodine deficiency
CRETINISM
tests for phenylketonuria
-This is done also to differentiate if the problem is either cretinism or a condition that involves an aminoacidopathy
phenylketonuria
Guthrie test
Characterized with problems not involving the T3 and T4, but rather directly involves the thyroid
stimulating hormone which regulates the hormones
➢ caused by TSH (thyrotrophin) deficiency
SECONDARY HYPOTHYROIDISM
➢ an enlarged thyroid gland which is a symptom of many thyroid disorders (hypo, hyper, or euthyroid state)
▪ It may cause deficiency or decrease in function, overactivity or hyper, or may be in euthyroid state
GOITER
pertains to nonthyroidal illness where abnormal thyroid function test with normal thyroid gland is observed
- Usually seen in critically ill or hospitalized patients
▪ Their thyroid gland is normally
functioning, but the level of their thyroid function test is abnormal
Euthyroid state
Another hormone produced by the thyroid gland
↑ Regulates calcium
↑ Release of calcitonin by the parafollicular cells is
stimulated if there is hypercalcemia
➢ Produced by parafollicular cells
➢ Involve in calcium deposition
➢ Marker for medullary thyroid cancer
CALCITONIN
- increased plasma Ca2+ concentration stimulates the
parafollicular cells of the thyroid to produce calcitonin
STIMULUS
– inhibition of osteoclast
activity which decreases the plasma concentration
↑ The bone will keep the calcium in the osteoclast
Calcitonin action on bone
– increased urinary excretion of Ca2+ (as well Na+ and PO43-)
which again decreases the plasma concentration
Calcitonin action on the kidneys
Gland posterior to the thyroid gland
* Four tiny glands attached to the thyroid
* Actions directed to bone, kidney, and intestines
* Controls calcium and phosphate metabolism with the
help of calcitonin
PARATHYROID GLAND
- releases ___
- is primarily responsible for maintaining Ca concentration by affecting activities of the
bone, kidney, and intestine - is released whenever the patient has hypocalcemia
↑ At the same time, it would also help in the activation of vitamin D to increase calcium in the blood circulation by facilitating its absorption in the small intestines while kidney reabsorbs calcium
PARATHYROID GLAND
- Parathyroid hormone (PTH)
synthesize and secrete
hormone PTH
Chief cells
non secretory cell
➢ seen only after puberty
Oxyphil cells
To prevent hypocalcemia (regulates blood calcium)
- is not released if the Ca level is normal
↑ It would only be released in cases of hypocalcemia
- Preserves calcium and phosphate within normal range
- * Promotes bone resorption
Stimulates inactive vitamin D to activated vitamin D3
↑ Helps incr
PARATHYROID HORMONE
Considered primary if the condition involves presence of adenoma in parathyroid gland
➢ The most common cause of
hypercalcemia
➢ Accompanied by phosphaturia
PRIMARY HYPERPARATHYROIDISM
Happens when there is an increase in the production of PTH in response to decrease serum calcium
➢ Diffuse hyperplasia of all 4 glands (parathyroid glands attached to thyroid gland)
➢ Patient develops severe bone disease
➢ Causes Vitamin D deficiency and chronic renal failure
SECONDARY HYPERPARATHYROIDISM
The body produces less than the normal PTH
Causes:
▪ Due to accidental injury to the parathyroid glands (neck) during surgery
▪ Can be idiopathic (unknown cause)
▪ Other cause:
▪ Autoimmune parathyroid destruction
* Individuals are unable to maintain calcium concentration in blood without calcium supplementation
HYPOPARATHYROIDISM
Where smooth muscle goes into auto contraction
- is the involuntary muscular spasm
* Can be used to observe where decreases in Ca2+ have occurred
- occurs if there is
hypocalcemia
TETANY
tetany in the hands can be induced by decreased Ca2+
↑ ____ is used to induce ischemia (about 20mmHg) for 3 minutes
to know if there would be carpopedal spasm
tROUSSEAU’S sign
- Sphygmomanometer
the facial nerve can be “tapped” to induce a muscle twitch
↑ This is performed by tapping the facial nerve about 2cm anterior to the external auditory meatus
cHVOSTEK’S sign
Calcium level < 6mg/dl
Laryngeal stridor & tonic- clonic
seizures
Calcium level < 8mg/dl
leads to tetany and
altered neuromuscular
activity
____ causes elevated bicarbonate
reabsorption (leading to ALKALOSIS)
Low PTH
dec ca and mg
tetany
Rickets
↑ Bone deformities is observed
Osteomalacia
Deficiency in vitamin D
PTH level measurement:
➢ Overnight fasting
PTH Related tests:
1
2
3
- Calcium
- Phosphorus
- Creatinine
