Week 11 - Thyroid Disorders Flashcards
where is the thyroid gland located
- wraps the anterior of the trachea just below the thyroid cartilage
what produces thyroid hormone or thyroxin
- cells arranged in circular patterns called follicles
what is thyroxin formed by
- 4 iodine atoms attached to 2 linked tyrosine amino acids
what hormone is released from the thyroid gland? how is it released?
T4 (tetraiodothyronine & thyroxin)
- released mostly inactive
what is T4 converted to? where does it occur?
- its active form = T3 (triiodothyronine)
- in the liver, kidneys, and other peripheral tissues
what happens to T3 once T4 is converted
- enters most cells and binds to an intracellular receptor similar to steroid hormones
the thyroid gland in the only tissue in the body that uses ______; what is it used for
- uses iodine
- used for synthesis of thyroid hormones
describe the negative feedback loop that plays a role in thyroid regulation
- the hypothalamus releases thyrotropin releasing hormone (TRH)
- TRH acts on the anterior pituitary to release thyroid stimulating hormone (TSH)/thryotropin
- TSH travels to the thyroid hormone to increase the production & secretion of thyroxin
- elevated lvls of thyroid hormone act in a negative feedback loop to inhibit TRH and TSH secretion
besides increasing the production & secretion of thyroxin, what else does TSH do
- acts as a growth factor to thyroid tissue
what is euthyroid
- state of having normal thyroid function
what are 2 hyper disorders of the thyroid gland
- hyperthyroidism
- thyroid storm
what are 2 hypo disorders of the thyroid gland
- hypothyroidism
- myxedema coma
what 3 things does the thyroid gland produce?
- T4
- T3
- calcitonin
what is the main fnxn of the thyroid gland
- production, storage, and release of T4 and T3
what is a goiter
- an abnormal enlargement of the thyroid gland
what is a nodule
- localized & palpable deformity of the thyroid gland which can be benign or malignant
what usually causes a goiter
- increased secretion of TSH or activation of the TSH receptor in the thyroid gland
do goiters occur in hypo or hyperthyroidism
- can occur in both
what are 2 types of goiters
- endemic
2. toxic
what is an endemic goiter
- goiter that occurs due to deficiency of iodine in the diet
how does iodine deficiency cause an endemic goiter
- causes a decreased production of thyroxin, leading to hypothyroidism
- hypothyroidism causes a compensatory & prolonged increase in TSH secretion leading to excess growth of the thyroid gland
what is a toxic goiter
- a goiter that continues to grow in the absence of TSH stimulation & hypersecrete thyroid hormone
what is a toxic goiter the result of
- dysplastic transformation of the thyroid cells that do not respond to TSH
what are goitrogens
- substances that can cause goiters by interfering w iodine uptake in the thyroid gland
list 4 drugs that are goitrogens
- iodine in large doses
- salicyclates
- sulphonamides
- lithium
(see notes for more)
thyroid nodules can be…. (3)
- benign
- malignant
- functional
what is a functional nodule
- nodule causes by elevated TSH
what is a concern with enlargement if the thyroid gland or thyroid nodules
- can cause tracheal compression if they become too large
what type of pt is thyroid cancer often founnd in
- an euthyroid pt
what are 2 risk factors for thyroid cancer
- exposure to ionizing radiation
- thyroiditis
what symptoms may occur during thyroid cancer (3)
- presence of painless, palpable nodules in an enlarged thyroid gland
- symptoms of hypo & hyper thyroidism
what are 2 categories of treatment for thyroid cancer
- surgical removal
- radiation therapy
describe surgical removal for thyroid cancer
may range from:
- unilateral total lobectomy with removal of the isthmus
- to total thyroidectomy w bilateral lobectomy
when is radiation used for thyroid cancer
- either as the primary treatment
- or as palliative treatment for pts w metastatic thyroid cancer
what parts of the body does T3 and T4 effect
- all body tissues
- plays a major role in our energy and BMR
what parts of the body does calcitonin effect
- bone tissue
what is hypothyroidism
- insufficient thyroid hormone
what are 2 types of hypothyroidism
- cretinism = congenital hypothyroidism
2. myxedema = adult or late onset hypothyroidism
describe the growth & development of a fetus w congenital hypothyroidism; why does this happen
- development if often normal
- bc T3 can cross the placental barrier from the maternal blood supply
what is required after birth for a newborn w congenital hypothyroidism
- supplementation for normal CNS development & bone growth
what causes myxedema (late or adult onset hypothyroidism)
- autoimmune destruction of the thyroid cells called Hashimoto’s thyroiditis
what does hashimoto’s thyroiditis cause (2)
- destruction of the thyroid cells causes a decrease in thyroxin secretion & a compensatory increase in TSH leading to goiter formation
- myxedema
what is myxedema
- accumulation of polysaccharides & water in CT of the skin
what is a 3rd cause of hypothyroidism
- drug induced
ex. anesthetics, amiodarone, lithium
what type of symptoms do we see during hypothyroidism
- symptoms related to slowed metabolism
what CNS symptoms are present during hypothyroidism (7)
- slowed mentation
- fatigue
- lethargy
- slowed speech
- depression
- memory loss
- possible paranoia or psychosis
what effect does hypothyroidism have on reflexes
- causes delayed reflexes
what MSK symptoms are present during hypothyroidism (6)
- muscle fatigue
- decreased strength
- decreased endurance
- decreased exercise tolerance
- muscle cramps
- stiffness
what causes the MSK symptoms of hypothyroidism (2)
- decreased amt of mitochondria causes the muscle fatigue
- elevated blood creatine kinase causes muscle cramps & stiffness
what CVS symptoms are present during hypothyroidism (5)
- bradycardia
- heartblock
- decreased CO
- cardiac dilation
- elevated LDL
what causes the CVS symptoms of hypothyroidism
- decreased production of myosin
- decreased alpha adrenergic receptors in the heart
- decreased LDL receptors in the liver
what impact does hypothyroidism have on the hematopoietic system (3)
- decreased erythropoiesis
- impaired absorption of vitamin B12
leading to anemia
what effect does hypothyroidism have on temp regulation (2)
- cold intolerance
- hypothermia
what resp symptoms are present during hypothyroidism
- decreased RR
- sleep apnea if left untreated
why does hypothyroidism cause decreased RR
- due to decreased CO2 production
what renal symptoms are present during hypothyroidism (2)
- decreased GFR = water retention
what causes the renal symptoms of hypothyroidism
- reduced renal blood flow
what GI symptoms are present during hypothyroidism
- constipation
what effect does hypothyroidism have on metabolism and how is it manifested (2)
delayed metabolism =
- weight gain despite loss of appetite
- myxedema = facial swelling, round cheeks
how does hypothyroidism impact the immune system
- causes susceptibility to infection
in severe cases, hypothyroidism can cause
- carotenemia = yellow pigmentation of the skin
what is one potential life-threatening complication of hypothyroidism
- myxedema coma
what is myxedema coma
- life-threatening coma caused by chronic untreated hypothyroidism
what is myxedema coma characterized by (4)
- hypothermia
- HF
- hypoventilation
- lactic acidosis
what can trigger a myxedema coma (2)
- cold exposure
- concurrent illness
in what cases does hypothyroidism not cause the “slow” symptoms (2)
- if caused by
1. thyroidectomy
2. antithyroid - sx will be insidious for months to years
how is hypothyroidism diagnosed (5)
- history
- physical exam
- blood test
- TPO antibodies
- others
what type of blood tests would we order for hypothyroidism
- T3
- T4
- TSH
what would be expected for blood works findings for hypothyroidism due to a problem w the thyroid
- low T4
- low T3
- high TSH (trying to compensate)
what blood work findings would be expected for hypothyroidism due to a problem w the hypothalamus
- low T4
- low T3
- low TSH
what are 4 other findings that may occur w hypothyroidism
- elevated cholestrol
- elevated triglycerides
- anemia
- increased creatine kinase
what med is given for hypothyroidism
- levothyroxone (synthroid)
what is levothyroxone
- synthetic T4
what is the MOA of levothyroxone
- replaces what the thyroid gland cannot produce to achieve normal thyroid levels
= works the same way as normal T4
what are 3 indications for levothyroxone
- primary hypothyroidism
- myxedema coma
- simple goiter
what reduces levothyroxone absorption
- food
- drugs
what implication does levothyroxone absorption being reduced by food have
- should be taken on an empty stomach in the morning ~30-60 min before breakfast
what 6 drugs reduce the absorption of levothyroxone
- H2 receptor blockers
- proton pump inhibitors
- antacids
- sucralfate
- aluminum containing antacids
- calcium supplements (tums)
describe the half life, plateau, and dosing of levothyroxone
- half life = 7 days
- once-a-day dosing & may have to be adjusted
- takes ~1 month to reach plateau
what does levothyroxone enhance the effect of
warfarin
= dosing may have to be adjusted
what can acute overdose of levothyroxone cause
- thyrotoxicosis (hyperthyroidism) = may have to be adjusted
what can chronic overdose of levothyroxine cause (2)
- accelerated bone loss
- increased risk of afib
(especially w older adults)
what is the goal in treatment of hypothyroidism
- restore a euthyroid state
what is treatment for hypothyroidism
- levothyroxine
- low calorie diet to promote weight loss
how long does a pt have to be on levothyroxine
- forever
what should we assess for during treatment of hypothyroidism
- ongoing symptoms
- worsening symptoms
- symptoms of hyperthyroidism
what is hyperthyroidism
- excessive amt of thyroid hormone
what is hyperthyroidism often caused by (5)
- autoimmune mechanisms
- thyroid cell transformation
- endemic goiters & hypothyroidism treated w iodine supplements
- pituitary adenoma
- hypothalamic disease
what is an example of how autoimmune mechanisms cause can hyperthyroidism? describe what happens
grave’s diseases
- an antibody that is formed binds to & activates the TSH receptor on cells
- the antibody mimics the effect of TSH resulting in hyperthyroidism
describe plasma TSH lvls in hyperthyroidism
- very low due to the negative feedback mechanism
overtime, hyperthyroidism causes by autoimmune mechanisms can lead to
- autoimmune destruction of the thyroid & hypothyroidism
grave’s disease & hasimoto’s thyroiditis are often associated w other autoimmune diseases like… (5)
- type 1 DM
- pernicuous anemia
- lupus
- RA
- myesthenia gravis
what are 2 examples of how thyroid cell transformation can cause hyperthyroidism
- endemic goiter
2. follicular adenoma (thyroid cancer)
what causes an endemic goiter & follicular adenoma and explain how this can cause hyperthyroidism
- both caused by transformed cells that do not respond to TSH & hypersecrete TSH
describe how an endemic goiter & hypothyroidism treated w iodine supplement can cause hyperthyroidism
- when iodine supplements are given to a pt w an endemic goiter or hypothyroidism, T4 synthesis is greatly increased = temporary hyperthyroidism
how does pituitary adenoma (cancerous growth) and hypothalamic disease cause hyperthyroidism
- can cause overproduction of TRH or TSH
what are symptoms of hyperthyroidism r/t (3)
- increased metabolism
- sensitivity to stimulation from SNS
= “fast” symptoms
what CVS symptoms are present during hyperthyroidism (7)
- increased CO
- increased HR & contractility
- widened pulse pressure
- afib
- supraventricular tachycardia
- premature beats
- cardiac hypertrophy
what can the rapid & strong HR during hyperthyroidism lead to
- exhaustion & HF
what resp symptoms are present during hyperthyroidism (3)
- tachypnea
- dyspnea
- resp failure
what causes the resp symptoms of hyperthyroidism
- tachypnea = d/t increased metabolic rate
- dyspnea & resp failure = d/t weakness & atrophy of resp muscles
what CNS symptoms are present during hyperthyroidism (8)
- rapid mentation
- anxiety
- nervousness
- irritability
- mania & psychosis
- poor conc
- insomnia
- rapid thoughts/speech
what effect does hyperthyroidism have on reflexes (2)
- tremor
- hyperactive deep tendon reflex
what MSK symptoms are present during hyperthyroidism (3)
- muscle atrophy & wasting (weight loss)
- weakness
- bone reabsorption exceeds bone formation
why does weight loss occur during hyperthyroidism? how does hyperthyroisism effect appetite
- due to increased metabolic rate
- appetite increases
why does muscle weakness occur during hyperthyroidism (3)
- due to inreased protein catabolism
- changes in myosin
what effect does bone reabsorption exceeding bone formation have during hyperthyroidism (3)
- hypercalcemia
- hypercalcuria
- osteoporosis
what effect does hyperthyroidism have on temp regulation (4)
- heat intolerance
- increased temp
- increased heat dissipation
- hot
what digestive & metabolic symptoms are present during hyperthyroidism (6) how does it effect BG, lipids, etc.
- rapid glucose absorption = BG rise (but often returns to normal)
- glucosuria (temp)
- LDL low
- adipocyte lipolysis increases
- FA rapidly metabolized
- vitamin deficiencies common
what impact does the rapid glucose absorption during hyperthyroidism have on DM pts
- may have increased insulin requirements
why is LDL low during hyperthyroidism
- due to increased hepatic LDL receptors
what GI symptoms are present during hyperthyroidism
- diarrhea
- defacation
what impact does hyperthyroidism have on menstrual cycles
- can cause menstrual irregularities & inferility
what does hyperthyroidism cause that relates to the eyes (2)
- exophthalamus/proptosis = bulging, wide eyes
- pretibial myxedema (this doesn’t relate to the eyes lol idk why i put this here)
why does exopthalamus occur during hyperthyroidism
due to:
- increased sympathetic tone
- orbital soft tissue becomes inflamed, edematous, and infiltrated w lymphocytes
what is pretibial myxedema? what does this occur w
- pretibial skin becomes thick & resembles an orange peel
- occurs w grave’s disease
how is hyperthyroidism diagnoses (4)
- history
- physical exam
- blood test
- RAIU
what can we get a blood test for during hyperthyroidism
- T4
- TSH
- T3 if needed
what blood test findings would be expected for hyperthyroidism d/t a problem w the thyroid
- high T4
- high T3
- low TSH (due to negative feedback)
what blood test findings would be expected for hyperthyroidism d/t a problem w the pituiatry or hypothalamus
- low TSH
- high T4
- high T3
what is a RAIU
- radioactive iodine uptake test
describe how an RAIU works
- radioactive iodine is given in oral form, circulates thru the body & is taken up by the thyroid in different amts depend on the thyroid disease
how is hyperthyroidism treated (4)
- drug therapy
- nutritional therapy
- radioactive iodine therapy
- surgical therapy
what are types of drug therapy for hyperthyroidism (2)
- beta blockers
- thionamides (antithyroids)
what is a type of antithyroid used for hyperthyroidism
- methimazole (tapazole)
what is the MOA of methimazole
- suppresses synthesis of thyroid hormone
how long might it take to become euthyroid on methimazole? why?
- 3-12 weeks
- bc it does mot destroy store of thyroid hormone
what are indications for methimazole (3)
- graves disease
- adjunct to radiation therapy
- prior to surgery
what is the half life of methimazole? how does this effect dosing>
- 6-13 hr = half life
= once/day dosing
describe the side effects of methimazole
- generally well tolerated
- may cause hypothyroidism
who should methimazole be avoided in? why?
- pregnancy women
- can cause neonatal hypothyroidism
what is the most dangerous toxicity associated w methimazole
- angranulosytosis = reduction in circulating granulocytes
what are signs of agranulocytosis? what should we monitor for?
- sore throat
- fever
monitor for signs of infection & CBC
is the agranulocytosis associated w methimazole reversible?
- yes once med is stopped
what beta blockers is often used for hyperthyroidism
- propanolol
what effect does propanolol have for someone w hyperthyroidism
- provides symptom relief r/t high beta adrenergic stimulation from thyroid hormones
when should propanolol not be used? why?
- if a pt has COPD, asthma, or HF
what BB should be used as replacement for propanolol if a pt has COPD, asthma, or HF
- metaprolol, atenolol (bc they are selective)
when is iodine used during hyperthyroidism
- short term prior to surgery or in crisis
what effect does iodine have on a pt w hyperthyroidism
- rapidly inhibits T3 and T4 synthesis
- decreases vascularity of thyroid gland
what is radioactive iodine used in
- graves disease
what is the effect of radioactive iodine
- destroys thyroid tissue to suppress thyroid hormone production
what is a common adverse effect of radioactive iodine
- excessive destruction can cause hypothyroidism
who cannot have radioactive iodine
- pregnant women
what is a type of surgical therapy for hyperthyroidism
- subtotal thyroidectomy –> significant part of the thyroid gland
what is included in nutritional therapy for hyperthyroidism (3)
- high calorie for hunger & prevention of tissue breakdown
- protein allowance
- avoidance of certain foods
what is the protein allowance for an individual w hyperthyroidism
- 1-2 g/kg of ideal body weight
what foods should someone w hyperthyroidism avoid (3)
- caffeine
- highly seasoned foods
- high fibre foods
to decrease abdom pain
what should you assess during ongoing treatment for hyperthyroidism (3)
- ongoing symptoms
- worsening symptoms & associated stressors
- symptoms of hypothyroidism
what is an emergency complication associated w hyperthyroidism
- untreated hyperthyroidism can lead to a thyroid crisis or storm
what typically precipitates a thyroid crisis or storm (3)
- concurrent illness
- trauma
- surgery
what are manifestations of a thyroid storm (8)
uncontrollable hyperthyroidism
- tachycardia or tachyarrythmia
- angina
- symptoms of HF
- fever
- NV
- diarrhea
- restlessness
- psychosis
what should you assess during inspection of the thyroid gland (2)
- size
- nodules
what should you auscultate during assessment of the thyroid gland
- any bruits? (may be heard during hyperthyroidism due to increased CO)
what should you palpate for during assessment of the thyroid gland
- tenderness
- nodules
- shape
what should you assess during history aspect of thyroid assessment (9)
- PMHx
- FMx
- any autoimmune disorders?
- PSHx
- Meds
- allergies
- immigration from an iodine deficient area?
- reproductive & menstrual history
- OPQRSTU & RoS of current symptoms
what should you assess during the physical exam for thyroid assessmentq
- vitals
- general h2t
- head, neck, eyes
- integ
- resp
- cvs
- abdom
- thyroid gland
