Thyroid Disease Flashcards
1
Q
Hashimoto’s Thyroiditis
A
- also known as chronic autoimmune thyroiditis
- it is the most common cause of hypothyroidism in adults
- caused by antibodies to thyroid peroxidase (anti-microsomal/TPO antibodies) and thyroglobulin
- TSH is appropriately elevated in response to low T3/T4
2
Q
How does hypothyroidism present?
A
insidious onset of…
- weight gain despite lowered appetite
- cold intolerance
- hyperactivity, lethargy, fatigue, weakness
- constipation
- diminished reflexes with slowed relaxation
- hypothyroid myopathy (proximal muscle weakness with increased creatine kinase)
- facial and periorbital myxedema
- dry, cool skin with coarse, brittle hair
- bradycardia and dyspnea upon exertion
- hypercholesterolemia due to diminished expression of LDL receptors
3
Q
What is subclinical hypothyroidism?
A
the absence of symptoms, normal free T4, and elevated TSH
4
Q
Levothyroxine
A
- an oral formulation of T4
- must be taken on an empty stomach at least one hour away from food
- initial therapy begins with 1.6 mcg/kg
- half life is seven days
- must beware when prescribing to those with advanced age or heart disease; start at a lower dose and gradually titrate
- binds to calcium and iron, reducing absorption
- re-evaluate dose at 8 week intervals until stable and then every 6-12 months there after
5
Q
Triiodothyronine
A
- an oral formulation of T3
- given at substantially lower doses than levothyroxine
- less commonly used than levothyroxine because it only has a half life of one day
6
Q
How does estrogen impact thyroid hormone?
A
- it increases levels of thyroid binding globulin, reducing the amount of bioavailable hormone
- a healthy thyroid will compensate by increasing production and the net result will be an increase in total T3/T4 but no change in the amount of bioavailable hormone
- someone with hypothyroidism, however, will need larger doses of levothyroxine
7
Q
How do androgens impact thyroid hormone?
A
it decreases levels of thyroid binding globulin, increasing the amount of bioavailable hormone
8
Q
How do glucocorticoids impact thyroid hormone?
A
it decreases levels of thyroid binding globulin, increasing the amount of bioavailable hormone
9
Q
How do salicylate and furosemide impact thyroid hormone?
A
they displace thyroid hormone from thyroid binding globulin, increasing the amount of bioavailable hormone
10
Q
Which substances are known to decrease the absorption of thyroid hormone or T4?
A
- cholestyramine
- colestipol
- PPIs
- raloxifene
- iron and calcium
- bran, soy, coffee
11
Q
What are the symptoms of hyperthyroidism?
A
- enlarged, homogenous (no nodules) thyroid with a bruit during auscultation
- weight loss despite increased appetite
- heat intolerance
- hyperactivity, anxiety, insomnia, hand tremor
- diarrhea
- brisk reflexes
- thyrotoxic myopathy (proximal muscle weakness with normal creatine kinase)
- pre-tibial myxedema and periorbital edema
- exophthalmos, lid lag ophthalmoplegia, conjunctivitis, altered visual acuity, and corneal ulceration
- warm, moist skin with fine hair
- chest pain, palpitations, arrhythmias due to an increase in number and sensitivity of beta-adrenergic receptors
- hypocholesterolemia due to elevated LDL receptor expression
12
Q
Graves Disease
A
- the most common cause of hyperthyroidism
- an autoimmune disorder characterized by IgG that activate TSH receptors on thyroid cells
- labs include decreased TSH, increased T3/T4, increased radioactive iodine uptake (RAIU), and positive tests for thyroid stimulating antibodies
- beta blockers and calcium channel blockers are used to treat symptoms
- radioactive iodine can be used to ablate the thyroid but thioamides, which inhibit thyroid hormone synthesis are more common today
13
Q
Thioamides
A
- a group of drugs that inhibit thyroid hormone synthesis by blocking iodination of the tyrosyl groups and coupling of iodotyrosines
- first line therapy for Grave’s disease
- propylthiouracil has a short half life; methimazole has a longer one and is use more often
- rash is the most common side effect but is tolerable
- may cause significant bone marrow depression, especially in patients over 40 or with doses of more than 40 mg/day, so monitor their CBC
14
Q
How is iodide used in the treatment of hyperthyroidism?
A
- once used to inhibit organification and hormone release
- but it has the potential to precipitate hyperthyroidism in those with existing thyroid disease
- no longer used therapeutically except in cases of thyroid storm refractory to thioamide
- it’s primary role is in nuclear emergencies to block the effects of radioactive iodine isotopes from damaging the thyroid
15
Q
Toxic Nodular Goiter
A
- hyperthyroidism caused by hyper functioning of a thyroid nodule
- may develop from a long-standing simple goiter
- more common in the elderly than Graves disease
- PE typically reveals an enlarged, nodular thyroid
- unlike Grave’s disease, ophthalmopathy and dermopathy are usually absent
- labs show decreased TSH, increased T3/T4, an absence of thyroid stimulating immunglobulins, and the RAIU shows a focal area of increased uptake
- treatment involves radioactive iodine ablation, thioamides, or surgery
