Wk5 Hypothyroidism Flashcards
Ture or False: 95% pf hypothyroid cases are due to primary hypothyroidism.
True
What is iatrogenic hypothyroidism?
Thyroid dysfunction caused by medical examination or treatment.
Does resistance to thyroid hormone commonly occur?
No, very rare.
What are the two common cause of hypothyroidism?
iodine deficiency and autoimmunity.
excessive or insufficient iodine can both lead to hypothyroidism.
What is the most common cause of hypothyroidism in North America?
Autoimmunity hypothyroidism
Under the category of autoimmunity hypothyroidism, what are the two subtype?
Hashimoto thyroiditis –most common
De Quervain disease (subacute granulomatous thyroiditis) — rare
What is the most common cause of central hypothyroidism?
Pituitary adenomas
What are the two main contributions to the symptoms of hypothyroidism?
- generalized slow metabolism
- polysaccharides accumulation in interstitial spaces
When should we refer our patient to fine-needle aspiration biopsy in the condition of goiter?
If there’s the presence of nodule
How is goiter diagnosed?
Ultrasound (assess the size and structure of the thyroid)
Under which condition, would surgery be needed on goiter?
If the enlargement causes difficulty breathing, swallowing or hoarseness.
Most goiters are euthyroid, hypothyroid or hyperthyroid?
Euthyroid (normal thyroid function)
True or False: goiter can be physiologic which is seen in adolescence and pregnancy due to increased thyroid demands.
True
Can goiter be a symptom of hyperthyroidism?
YES. In condition such as Grave’s disease, toxic nodular/multinodular goiter, thyroid cancer or infiltrative disease.
True or false: goiter can be a symptom of inflammatory disorders — autoimmune, postpartum, silent, radiation, subacute, suppurative.
True.
What is goiter due to iodine deficiency called?
Endemic goiter
Which symptom do patient experience most frequently in hypothyroidism?
Tiredness (sensitivity of 81%)
Which symptoms if present, significantly increase the likelihood of autoimmune hypothyroidism?
Anterior neck pain
Which symptom, if is absent, decrease the likelihood of autoimmune hypothyroidism?
Tiredness
As the autoimmune hypothyroidism progress, which two symptoms are relatively more common?
Drier skin & poorer memory
In progressive autoimmune hypothyroidism, which symptom, if present, significantly increase the likelihood of autoimmune hypothyroidism?
Feeling colder
True or False: When diagnosing thyroid-related symptoms, clinicians must differentiate between true thyroid dysfunction and other non-thyroidal causes that can mimic or co-exist with thyroid diseases, where TSH levels are normal but symptoms persist.
True
Can biotin interfere with laboratory testing of TSH, T4, T3?
Yes. Biotin can falsely cause high T4, high T3 and low TSH, which appear as hyperthyroidism or thyroid replacement dosing is too high.
True or False: Various non-thyroidal illnesses, medications, and external factors can lead to falsely elevated TSH or falsely low T4/T3 levels, potentially mimicking thyroid dysfunction.
Ture. These factors must be considered when interpreting thyroid function tests to avoid misdiagnosis and unnecessary treatment.
How long before thyroid function test should a patient avoid biotin supplementation?
48hr.
What does St johns wort do to thyroid function test?
Falsely elevate TSH
Low TSH should indicate hyperthyroid state or hypothyroid state?
Low TSH & high T3, T4 —> hyperthyroidism
What is central hypothyroidism? Is thyroid normal ? is pituitary or hypothalamus normal?
Central hypothyroidism is due to insufficient stimulation to the thyroid gland.
Thyroid gland is normal, problems are in the pituitary gland or the hypothalamus
What is the prevalence of central hypothyroidism?
Less than 1% of hypothyroid cases
What is the common cause of central hypothyroidism in children?
Common cause include brain tumor (craniopharyngiomas), crania irradiation…
What is the common cause of central hypothyroidism in adult?
Pituitary macroadenomas (noncancerous tumor in the pituitary), pituitary surgeries, or radiation therapy to the pituitary area.
Can over-replacement of T4 cause central hypothyroidism?
Yes. Patient with primary hypothyroidism who are receiving too much thyroid hormone replacement may develop temporary suppression of the pituitary.
Is the symptom of central hypothyroidism milder than primary hypothyroidism?
Yes. Because the lack of thyroid hormones develops slowly, allowing the body to partially adapt.
What would TSH and T4 look like in central hypothyroidism?
Low TSH and low T4
What is TRH stimulation test used for?
Evaluate central hypothyroidism in differentiating between secondary and tertiary hypothyroidism.
Is the prognosis of central hypothyroidism similar to primary hypothyroidism?
Yes
What does TSH and T4 look like in subclinical hypothyroidism?
Subclinical hypothyroidism: endocrine disorder
Elevated TSH but normal T4
What is the symptom presentation in subclinical hypothyroidism?
Most often asymptomatic or mild hypothyroid symptoms
What is the prevalence of subclinical hypothyroidism? Which population is affected more?
Higher prevalence in older patients (65+) or females and those with autoimmune thyroiditis.
3-15% general population
When would treatment for subclinical hypothyroidism be indicated?
- TSH over 10mIU/L
- Presence of TPO antibodies (evaluate autoimmune thyroiditis)
- Symptomatic
- cardiovascular risk factors (i.e. high cholesterol)
In subclinical hypothyroidism, if TSH is between 4.0 to 10 mIU/L, what is the next step?
Monitor TSH level every 6 to 12 months
If TSH is over 10 mlU/L, what are the associated risks?
Increased fracture, ischemic heart disease and heart failure
What is the prognosis of subclinical hypothyroidism?
Primary hypothyroidism (overt): 2-6%
Resolve without intervention: 60%
What does TSH and T4 look like in primary hypothyroidism?
Elevated TSH and low T4
Which population will be affected by primary hypothyroidism most?
Female, older population (65+), autoimmune disease (T1DM or celiac), Down or Turner syndrome
What is the prevalence of primary hypothyroidism in the US?
0.3%
Would anti-TPO help with the diagnosis of primary hypothyroidism?
No. It would be used to indicate autoimmune etiology.
What is the management plan for primary hypothyroidism?
Thyroid hormone replacement therapy (T4)
What is the prognosis of primary hypothyroidism?
Good prognosis with treatment. Without treatment, high risk of morbidity and mortality such as heart failure.
Does Canadian Task Force on Preventive Health Care (CTFPHC) recommend screening for thyroid dysfunction in asymptomatic nonpregnant adults?
No. CTFPHC strongly against screening
With the opinion on thyroid function screening from CTFPHC, what’s USPSTF’s opinion? (US Preventive Services Task Force)
Current evidence is insufficient to assess the balance of benefits and harms of screening for thyroid dysfunction in nonpregnant and asymptomatic adults.
What is the management plan for secondary hypothyroidism?
Brain MRI
What is the management plan for primary hypothyroidism?
Levothyroxine
This patient has normal T4 but TSH level is over 10mlU/L. There’s presence of thyroid antibodies and this patient has cardiovascular risk and treatment-resistant depression. What is the next step?
Consider levothyroxine
What is the requirement for thyroid hormone during pregnancy?
20-40% increase in thyroid hormone as early as 4 weeks.
- notable increase in thyroid gland size
*estrogen-mediated increase in TBG
*increased demand for thyroids hormone
How does TSH, T4 and T3 fluctuate during pregnancy?
TSH decrease in the first trimester due to stimulation to thyroid from hCG. TSH level normalized by the 2nd and 3rd trimesters as hCG decreases overtime
T4 decrease over the course of pregnancy due to increased TBG
T3 decrease over the course of pregnancy due to increased TBG
Pregnant women under which condition would have higher TSH?
Women who are thyroid antibody positive.
What is the prevalence of hypothyroidism in pregnancy?
0.3-0.5% of pregnancy: primary hypothyroidism
2-3% of pregnancy: subclinical hypothyroidism
What is the predominant cause of hypothyroidism in pregnancy?
Chronic autoimmune hypothyroidism
Is it safe to prescribe levothyroxine to women who is pregnant?
Yes. It can reduces the risk of miscarriage and preterm birth, improve fetal neurocognitive development but little to no effect on hypertension and placental abruption.
What is postpartum thyroiditis?
Abnormal TSH within first 12 months postpartum without toxic thyroid nodules or thyrotoxin receptor antibodies.
What is the risk population for postpartum thyroiditis?
Women with T1DM or TG/TPO autoantibodies.
What is the prevalence of postpartum thyroiditis?
8% on average but range from 1.1%-21.1%
What is the prognosis of postpartum thyroiditis?
Increased risk of permanent hypothyroidism
What are some symptoms of postpartum thyroiditis?
Fatigue
Hypothyroidism (high TSH)
Hyperthyroidism (Low TSH)
In both men and females who has hypothyroidism, which disease has a significantly elevated relative risk ?
Addison’s disease
How would you diagnose Addison Disease?
Low morning cortisol
2x high ACTH
Low Na+, high K+ and hypotension
What is the next step when Addison’s disease is suspected?
ACTH stimulation test
What is the prognosis of Addison’s Disease?
Up to 50% of patients with Addison’s disease may develop another autoimmune disease over time. If left untreated, patient may experience an adrenal crisis.
Which population will have a higher chance of developing Addison’s Disease?
30-50yrs of age
Females
other autoimmune disease
What is a classic sign of Addison’s Disease?
Hyperpigmentation
Can celiac disease co-exit with hypothyroidism?
Yes
Is Addison’s Disease an autoimmune disease?
YES. Adrenal insufficiency due to autoantibodies damaging adrenal cortex.
Would thyroid hormone replacement trigger adrenal crisis in unrecognized patients?
Yes. Low cortisol is unable to manage the increase metabolic demands from increased thyroid hormone.
Pain
V/D, dehydration, hypotension
loss of consciousness and death
When adrenal insufficiency is confirmed, what is the next step?
Thyroid test & treat adrenal insufficiency (primarily)
True or False: Overt hypothyroidism increase the risk for coronary artery disease.
True
What is the caution in treating hypothyroidism with heart disease?
Thyroid replacement therapy can increase heart rate & contractility which can precipitate acute coronary syndrome (reduced blood flow to the heart) or an arrhythmia (abnormal heart rhythms).
We need to start with low dosing of thyroid replacement and proceed slowly.
Does TSH increase with age? Does T4 increase with age?
TSH increases with age as the body’s regulation of thyroid function becomes less efficient with age.
T4 remains stable, indicating that the thyroid gland can still maintain normal hormone levels even with increased TSH.
Should thyroid replacement therapy start at lower or higher doses than in younger patients?
Lower due to the higher risk of heart problems in older adults if thyroid hormone is introduced too rapidly or in excessive amounts.
What is the life-threatening manifestation of hypothyroidism due to inadequate treatment?
Myxedema
Which population is more likely to experience myxedema?
Female over 60 in winter
What is the next step when myxedema is suspected?
ER
