Thyroid 2 Flashcards
Types and biosynthesis of thyroid hormones
-Synthesized in the thyroid gland by: ____ , Coupling of ______ molecules and Attaching to ______ protein
Iodination
two tyrosine
thyroglobulin
Thyroid gland mostly secretes ____
T4
Peripheral tissues (liver, kidney, etc.) iodinate T3 to T4 T/F
F
They deiodinate T4 to T3
___ is the more biologically active thyroid hormone
T3
T4 can be converted to rT3 (____ T3) ( an active or inactive form? )
reverse
Inactive
Most of T4 is transported in plasma as protein-bound
- Thyroglobulin-bound (___ %)
- Albumin-bound (___ %)
- Transthyretin-bound (__ %)
70
25
5
The unbound (free) form of T4 and T3 are biologically ____
active
Thyroid hormone action
-Essential for normal maturation and metabolism of all body tissues
T/F
T
Thyroid hormone action
Affects the rate of protein, carbohydrate and lipid metabolism
T/F
T
Thyroid hormone action
Regulates thermogenesis
T/F
T
Hypothyroid children have delayed skeletal maturation, tall stature, delayed puberty
T/F
F
Short
Untreated congenital hypothyroidism causes permanent brain damage
T/F
T
Hypothyroid patients have low serum cholesterol
T/F
F
High
Hypothyroid patients have High cholesterol due to (up or Down?)? regulation of ____ receptors on ___ cells and Failure of sterol ____ via the ___
Down
LDL
liver
excretion; gut
Regulation of thyroid hormone secretion
-The _____ axis regulates thyroid secretion
hypothalamic-pituitary-thyroid
The hypothalamus senses low levels of T3/T4 and releases _____
thyrotropin releasing hormone (TRH)
TRH stimulates the pituitary to produce _____
thyroid stimulating hormone (TSH)
TSH stimulates the thyroid to produce _____ until levels return to normal
T3/T4
T3/T4 exert _____ feedback control on the ____ and ____ to Control the release of ___ and ___
negative
hypothalamus and pituitary
TRH and TSH
High thyroid level _____ TRH and TSH
-Low thyroid levels ——- TRH and TSH to produce more hormone
suppress
stimulate
TSH measurement Indicates thyroid status
T/F
T
Total T4 or free T4 measurement can be used to Monitor anti-thyroid treatment and thyroid supplement treatment
T/F
T
In T4 treatments , TSH may take upto __ weeks to adjust to new level during treatment
8
TSH and T4 (total or free) are ensitive, first-line test
T/F
T
Some labs only measure TSH as first-line test
T/F
T
Total T3 or free T3:
*Rise in T3 is dependent of T4
T/F
F
It’s independent
For earlier identification of T3 thyrotoxicosis
- Antibodies:
- Diagnosis and monitoring of autoimmune thyroid disease
- Hashimoto’s thyroiditis
T/F
T
Goitre
-Enlarged thyroid gland May be associated with Normal function of thyroid gland
T/F
T
Causes of goiter
- ____ deficiency
- _____ deficiency
- ____ thyroiditis
- Congenital ____thyroidism
- _____’ disease (___thyroidism)
- ____ cancer
Iodine
Selenium
Hashimoto’s
hypo
Grave’s; hyper
Thyroid
Hypothyroidism -Primary hypothyroidism:Failure of \_\_\_\_ -Secondary hypothyroidism:Failure of the \_\_\_\_ to secrete TSH (\_\_\_) or Failure of the \_\_\_\_\_\_ axis
thyroid gland
pituitary; rare
hypothalamic-pituitary-thyroid
Hashimoto’s disease causes ____?
Hypo or hyper thyroidism
Hypo
Radioiodine or surgical treatment of hyperthyroidism can go wrong and lead to ____?
Hypo
Clinical features of hypothyroidism includes ____ skin
Dry
Diagnosis
Elevated TSH level confirms hypothyroidism
T/F
T
Treatment for hypothyroidism
-Patient has to continue treatment for a year
T/F
F
For ever
Neonatal hypothyroidism
- Due to ____ defect in thyroid gland of newborns
- Diagnosed by ____ screening
- Hormone replacement therapy
- May cause ____, if untreated
genetic
TSH
cretinism
Non-thyroidal illness
- In some diseases, the normal regulation of TSH, T3 and T4 secretion and metabolism is disturbed
- Most of T4 is converted to ____
- Causing thyroid hormone deficiency
- TSH secretion is ____
- Secretion of T4 and T3 is decreased
rT3
suppressed
Hyperthyroidism
-Tissues are exposed to high levels of thyroid hormones (______)
thyrotoxicosis
Causes of hyperthyroidism
- Graves’ disease
- _____ goitre
- Thyroid adenoma
- Thyroiditis
- Intake of iodine / iodine drugs
- Excessive intake of T4 and T3
Toxic multinodular
Clinical features of hyperthyroidism
- Weight ___ with ___ appetite
- Fatigue
- Palpitation / agitation, tremor
- Angina, heart failure
- Diarrhea
loss ; normal
Sweating / heat intolerance is a symptom of ____thyroidism
Hyper
Eyelid retraction and lid lag is a feature of ____thyroidism
Hyper
-Most common cause of hyperthyroidism is ____?
Grave’s disease
Graves’ disease is an autoimmune disease
T/F
T
In grave’s disease
Antibodies against _____ on thyroid cells mimic the action of _____ hormone
-Normal regulation of synthesis/control is disturbed
TSH receptors
pituitary
In grave’s disease
Diagnosis
- _____ TSH level
- _____ thyroid hormone level
Suppressed
Raised
Grave’s disease Confirms primary hyperthyroidism
T/F
T
Problems in diagnosis of grave’s disease
- Total serum T4 conc. changes due to changes in ______ level
- In pregnancy, high estrogens increase ____ synthesis
- Total T4 will be high
- Congenital TBG deficiency can also influence results
- _____ and ____ are first-line tests for thyroid dysfunction
binding protein
TBG
Free T4 and TSH
Treatment
- Antithyroid drugs: _____,_____
- Radioiodine: ______ inhibits T4/T3 synthesis
- Surgery: ___
carbimazole, propylthiouracil
sodium 131I
thyroidectomy
Thermogenesis
- About ___% thermogenesis depends on thyroid
- It ___eases ATP synthesis and consumption by many possible mechanisms
- ____ gradient requires ATP to maintain it
- The gradient is used to transport ___ inside the cell
- Thyroid reduces Na/K gradient across the cell membrane
- Causing more nutrient transport in the cell (increasing metabolism)
- This increases the demand for ATP to maintain the gradient
- ATP synthesis and consumption is increased that produce heat
- Thyroid hormones cause increased proton leak into the matrix across the inner mitochondrial membrane
- Protons are pumped back into the matrix by uncoupling proteins (UCPs) without ATP synthesis
- This process produces heat
- The mitochondria of brown adipose tissue contain UCP-1 (thermogenin)
- Produces heat via uncoupling of electron transport chain and oxidative phosphorylation
30
incr
Na/K; nutrients
Thyroid regulates metabolism and ATP turnover
T/F
T
The decrease in TBG levels results in a transient ___ease in the level of free thyroid hormones
incr
a consequence of increased free thyroid hormone is (inhibition or stimulation ?)of synthesis of thyroid hormones (by ____ feedback).
Inhibition
negative
during pregnancy, the high level of ____ inhibits _____ and __eases TBG levels.
estrogen
hepatic breakdown of TBG
hepatic breakdown of TBG
With a higher level of TBG, less thyroid hormone is free and unbound.
T/F
T
In pregnancy, as a consequence of all these changes, levels of total T4 and T3 are ___eased but levels of free, physiologically active, thyroid hormones are ___eased and the person is said to be “clinically _____.”
increased
Normal
euthyroid
____ converts T4 to T3 by removing one atom of I2 from the ____ ring of the molecule.
5′-iodinase
outer
The target tissues also convert a portion of the T4 to reverse T3 (rT3) by removing one atom of I2 from the ___ ring of the molecule
inner
thyroid hormones inhibit the synthesis of (i.e., upregulate) cardiac β1-adrenergic receptors.
T/F
F
They induce it
Drooping eyelids is a symptom of _____?
Hypo or hyper thyroidism
Hypo
The most common cause of hypothyroidism is _____ of the thyroid gland (thyroiditis)
auto-immune destruction
Ingestion of exogenous thyroid hormones, or _____ hyperthyroidism causes goiter or no goiter??
factitious
No goiter
