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Primary Care 3 > Thyroid Week 6 > Flashcards

Thyroid Week 6 Flashcards

1
Q

single best test for thyroid

A

TSH since the vast majority of cases of thyroid dysfunction are due to primary thyroid disease, to which the pituitary gland responds with predictable changes in TSH secretion

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2
Q

How do you interpret the serum TSH level?

A

if TSH is elevated, the patient almost always has primary hypothyroidism; when the TSH is low, the patient usually has primary hyperthyroidism

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3
Q

what labs change first if problem with the thyroid

A

Abnormal serum TSH values reflect mild thyroid dysfunction long before serum T 4 and T 3 levels are outside their reference ranges. Exceptions to these rules occur in patients who have pituitary-hypothalamic disorders or non-thyroidal illnesses. Measurement of serum free T 4 should be performed whenever the TSH level is high

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4
Q

why do we give thyroid replacement.

A

either replacement therapy for hypothyroidism or suppression therapy (lower than normal) for thyroid cancer

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5
Q

Free T 4 and T 3 assays determine what?

A

the amounts of unbound, bioactive thyroid hormones in the circulation

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6
Q

T4 aka

A

thyroxine, made by thyroid

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7
Q

T3 aka

A

triiodothyonine, made by thyroid

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8
Q

Serum free thyroxine (T 4 ) should be measured in ?

A

all patients whose TSH is elevatedand serum free T 4

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9
Q

serum free T 4 and total triiodothyronine (T 3 ) or free T 3

A

measured in patients whose TSH is suppressed

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10
Q

Anti- TPO (thyroid peroxidase) antibodies are the most accurate test to establish a diagnosis of ?

A

chronic lymphocytic thyroiditis (Hashimoto’s disease)

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11
Q

Serum thyroglobulin (TG) is useful for monitoring ?

A
  • for recurrence of differentiated thyroid cancer and

- for assisting in the diagnosis of destructive thyroiditis

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12
Q

Radioactive iodine uptake (RAIU) is used primarily to ?

A

determine whether patients with thyrotoxicosis have a high-RAIU or low-RAIU disorder

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13
Q

A thyroid scan is used mainly to ?

A

distinguish among the three most common types of high-RAIU thyrotoxicosis: Graves ’ disease, toxic multinodular goiter, and a solitary toxic adenoma

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14
Q

most common world wide cause of hypothryoidism

A

iodine deficiency, need iodine to make T3 (poorer countries) but in developed countries- Hashimoto’s

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15
Q

The three most common causes of hyperthyroidism are

A

Graves’ disease, toxic multinodular goiter, and toxic adenoma

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16
Q

Thyrotoxicosis is the general term for what?

A

the presence of increased levels of thyroxine (T 4 ), triiodothyronine (T 3 ), or both, from any cause

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17
Q

whereas, hyperthyroidism refers to

A

causes of thyrotoxicosis in which the thyroid is actively overproducing thyroid hormone

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18
Q

Subclinical thyrotoxicosis is defined as ?

A

low serum TSH level with normal free T 4 and T 3

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19
Q

What is Graves’ disease ?

A

an autoimmune disorder in which activating autoantibodies directed against the TSH receptor result in continuous stimulation of thyroid hormone production and secretion as well as thyroid growth (goiter)

20
Q

Extrathyroidal manifestations of Graves’ disease include what?

A

ophthalmopathy (proptosis, periorbital edema, extraocular muscle dysfunction, and optic neuropathy), dermopathy (pretibial myxedema), and thyroid acropachy (digital clubbing and edema)

21
Q

what is a toxic multinodular goiter?

A

TMNG generally arises in the setting of a long-standing multinodular goiter in which certain individual nodules have developed autonomous function and secrete thyroid hormone independent of stimulation by TSH

22
Q

What are autonomously functioning thyroid nodules?

A

AFTNs, or toxic adenomas, are benign tumors that have either constitutive activation of the TSH receptor or its signal-transduction apparatus. These tumors frequently produce subclinical thyrotoxicosis and have a predilection for spontaneous hemorrhage.

23
Q

What is the Jod-Basedow phenomenon?

A

The Jod-Basedow phenomenon is iodine-induced thyrotoxicosis following exposure to large quantities of iodine (typically in iodinated radiographic contrast agents for CT or angiography, but also with the antiarrhythmic drug amiodarone)

24
Q

TRH- thyroid releasing hormone made where?

A

hypothalamus. TRH goes to pituitary to tell the pituitary to make TSH thyroid stimulating hormone

25
Q

thyroid hormone is highly bound to what?

A

plasma proteins (99%) so that means total thyroid hormone concentration is affected by levels of plasma proteins, so clinically we should measure FREE T4 (not total)

26
Q

what is autoimmune thyroiditis ?

A

aka Hashimotos. it’s characterized by inflammation/ destruction of thyroid follicular cells - immune system is attacking the thyroid as if it was a foreign invader.

27
Q

what are the markers for Hashimotos

A

antiperoxidase and antithyroglobulin

28
Q

Grave’s disease

A

characterized by antibodies that stimulate the TSH receptor, so you have an excess of thyroid hormone

29
Q

3 most common causes of hyperthyroidism

A

Grave’s disease
Toxic multinodular goiter (TMNG)
Toxic adenomas or autonomously functioning thyroid nodules (AFTNs)

30
Q

how does hyperthyroidism cause eye disease

A

Lid retraction and stare can be seen with any cause of thyrotoxicosis and are due to sympathetic/adrenergic overactivity. True ophthalmopathy or orbitopathy is unique to Graves’ disease

31
Q

What laboratory testing should be performed to confirm thyrotoxicosis?

A

Measurement of serum TSH with a third-generation assay (with detection limits of 0.01 mU/L) is the most sensitive means of detecting thyrotoxicosis.

32
Q

When is thyroid antibody testing needed in patients with hyperthyroidism?

A

The cause of hyperthyroidism can usually be determined with history, physical examination, and radionuclide studies. Testing for TSH receptor antibodies can be used to diagnose Graves’ disease during pregnancy, when radionuclide imaging is contraindicated.

33
Q

How should hyperthyroidism be treated?

A

The three main treatment options are antithyroid drugs (ATDs), radioiodine ( 131 I) ablation, and surgery.

34
Q

antithyroid drugs (ATD’s)

A

methimazole and propylthiouracil. Methimazole is almost always the preferred agent. Only use propylthiouracil in 1st trimester of preggo bc can’t concerns of hepatotoxicity

35
Q

what drugs to help relieve sx of hyperthyroid?

A

most patients should receive beta-blockers (unless contraindicated) for heart rate control and symptomatic relief. Propanolol most commonly used.

36
Q

Thyroiditis can cause severe ?

A

thyrotoxicosis but generally resolves without intervention and may be followed by a hypothyroid phase

37
Q

Routine diagnostic testing for hyperthyroidism includes ?

A

measurements of serum thyroid-stimulating hormone (TSH), free T 4 , T 3 , radioactive iodine uptake testing, and thyroid scanning with 123 I or technetium 99m Tc.

38
Q

Treatment is generally indicated in all patients in whom ?

A

TSH is less than 0.1 mU/L

39
Q

What is the role of iodine in the treatment of hyperthyroidism? What is the Wolff-Chaikoff effect?

A

Inorganic iodine rapidly decreases the synthesis and release of T 4 and T 3 . The transient inhibition of thyroid hormone synthesis by excess iodine is known as the Wolff-Chaikoff effect. However, because this effect generally lasts for about 10 to 14 days, iodine is usually used only after ATDs have been started, to prepare a patient rapidly for surgery, or as an adjunctive measure in patients with thyroid storm.

40
Q

Which medications block peripheral conversion of T 4 to T 3 ?

A

Propylthiouracil, propranolol, glucocorticoids, iopanoic acid, and amiodarone inhibit the peripheral conversion of T 4 to T 3 .

41
Q

How effective are ATDs in treating hyperthyroid?

A

90% of patients taking ATDs become euthyroid without significant side effects. Approximately 1/2 of patients attain a remission from Graves’ disease after a treatment course of 12 to 18 months. If doesn’t go away or comes back prob will need surgery

42
Q

What side effects are associated with ATDs?

A
  • agranulocytosis is a rare but life-threatening complication. Pts on these meds need to report a fever, sore throat ASAP- go straight to ED
  • sometimes hepatotoxic (tell pts to report rt upper quadrant pain, nausea, new pruritis)
  • Potential teratogenicity (so-called methimazole embryopathy)
43
Q

What laboratory tests should be monitored in patients taking ATDs?

A

Serum free T 4 and T 3 levels should be remeasured about 4 weeks after initiation of an ATD, and the dose adjusted accordingly. Because TSH may remain suppressed for several months, free T 4 and T 3 levels are more reliable for assessing thyroid hormone status during this time.

44
Q

How does radioactive iodine work?

A

delivers killing dose of radiation to thyroid cells only- little exposure elsewhere. Given once orally and then hypothyroidism usually ensues over next 3- 6 mos. Also can’t be preggo- pregnancy should be deferred for at least 4 to 6 months after

45
Q

What is the preferred initial treatment for hypothyroidism?

A

Levothyroxine (LT 4 )- in healthy young patients can start at a dose of 1.6 mcg/kg/day.

46
Q

The goal TSH for treatment of primary hypothyroidism is?

A

between 0.5 and 2.0 mU/L

47
Q

Subclinical hypothyroidism is ?

A

elevated TSH but normal thyroxine/triiodothyronine (T 4 /T 3)- treatment can alleviate symptoms as well as cardiac and lipid abnormalities

Primary Care 3 (29 decks)

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