Endo-Thyroid

Question 1

What else should you measure if TSH is high? If it’s low?

Answer 1

If the serum TSH level is frankly abnormal, additional evaluation of thyroid function should be considered to determine the extent of the dysfunction. This is accomplished by measuring T4 when the TSH is elevated and by measuring T4 and T3 when the TSH is suppressed.

Question 2

What is the role of calcitonin in thyroid malignancies?

Answer 2

Calcitonin, secreted by the C cells of the thyroid, is most frequently used as a tumor marker in patients with a history of medullary thyroid carcinoma. Serum calcitonin levels can help increase the sensitivity of detection of medullary thyroid carcinoma when used in conjunction with fine-needle aspiration (FNA). However, it is not recommended as a screening test in all patients with thyroid nodules because it lacks the requisite specificity. Instead, measurement of calcitonin should be considered if a patient with thyroid nodular disease has a history of hyperparathyroidism or a family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2, or if there is clinical suspicion for these disorders.

Question 3

What is the purpose of radioactive iodine uptake?

Answer 3

Radioactive iodine uptake (RAIU) is a measure of iodine uptake by the thyroid over a pre-specified time frame, typically 24 hours. RAIU is used to evaluate the cause of hyperthyroidism; it is not indicated in patients with normal or elevated TSH levels.

Question 4

What is the radio iodine uptake pattern for:

• Graves Disease
• Toxic multi nodular goiter
• Thyroiditis
• Exposure to exogenous thyroid hormone

Answer 4

AIU percentage is typically very high in patients with Graves disease (diffusely increased uptake) and only moderately elevated in those with toxic multinodular goiter (patchy uptake in areas of nodules with relative suppression of normal tissue). In contrast, the RAIU is very low in those with thyroiditis or exposure to exogenous thyroid hormone.

Question 5

Who is radio iodine uptake contraindicated in?

Answer 5

RAIU is contraindicated during pregnancy and while breastfeeding.

Question 6

What are the signs and symptoms of thyrotoxicosis?

Answer 6

The symptoms of thyrotoxicosis include heat intolerance, palpitations, dyspnea, tremulousness, menstrual irregularities, hyperdefecation, weight loss, increased appetite, proximal muscle weakness, fatigue, insomnia, and mood disturbances.

Question 7

Typical pattern of hyperthyroidism with TSH, T3, T4?

What does a normal serum TSH in the setting of an elevated T4 and/or T3 concentration suggest?

Answer 7

The typical pattern of hyperthyroidism is TSH suppression with an elevated T4 and/or T3. A normal serum TSH in the setting of an elevated T4 and/or T3 concentration suggests the presence of a TSH-secreting pituitary adenoma; these tumors are extremely rare and are managed differently from other causes of thyrotoxicosis (see later discussion).

Question 8

Management of thyrotoxicosis?

Answer 8

1. beta blocker: propranolol, but preferably atenolol
2. Methimazole and PTU
3. Radioactive iodine ablation or surgery

Question 9

What is Grave’s Disease?

Answer 9

Graves disease is a multiorgan system autoimmune disorder that can affect the thyroid, eyes, and skin. It is frequently seen in women between the ages of 20 and 50 years and is the most common cause of hyperthyroidism in the United States. Antibodies against the TSH receptor (TSI or TRAb) stimulate autonomous production of T4 and T3. Patients frequently report a family history of Graves disease, Hashimoto thyroiditis, or other autoimmune conditions.

Question 10

Clinical features of Graves Disease

Answer 10

On physical examination, patients have elevated systolic blood pressure with a widened pulse pressure, tachycardia, and a diffusely enlarged thyroid. Further inspection of the thyroid may reveal a bruit. Careful examination of the skin may reveal pretibial myxedema, an infiltrative process that is typically patchy with a peau d’orange appearance to the skin.

Question 11

How is diagnosis of Grave’s Disease made?

Answer 11

Diagnosis of Graves disease is made clinically in most instances, and measurement of TSI antibodies is reserved for patients who are not markedly thyrotoxic on examination and do not have a classic smooth, rubbery, diffuse goiter. In those patients, TSI antibodies may help determine the cause of the hyperthyroidism. RAIU and scan will show markedly increased uptake with diffuse activity on the scan.

If ophthalmopathy is present, the patient may exhibit lid retraction (lid lag), whereby contraction of the levator palpebrae muscles of the eyelids results in immobility of the upper eyelid with downward rotation of the eye. Additionally, patients may have proptosis, scleral injection, and periorbital edema.

Question 12

During pregnancy, when do you use PTU and methimazole for Grave’s Disease?

Answer 12

PTU: 1st trimester
methimazole: after that

Therefore, its use is reserved for patients who cannot tolerate methimazole and during the first trimester of pregnancy, when methimazole has a possible teratogenic effect.

Question 13

How is a thyroid adenoma identified?

Answer 13

If a patient is suspected of having a toxic nodule, thyroid scintigraphy should be performed to determine if the nodule is autonomous. The thyroid uptake scan will reveal increased activity in the “hot” nodule with relative suppression of the remaining thyroid tissue. These results should then be correlated with the ultrasonographic findings to determine if any additional nodules exist, which will require further investigation with FNA.

Question 14

How is a thyroid adenoma treated?

Answer 14

Radioactive iodine ablation or surgery is the most common treatment for toxic thyroid nodules; indications for surgery include a large goiter with compression symptoms or concern for malignancy.

Question 15

What is destructive thyroiditis?

Answer 15

There are two phases. Thyrotoxic Phase is early on and lasts 2-6 weeks, patients demonstrate signs of thyrotoxicosis. Damage is caused to the thyroid so it cannot produce T3 and T4. The pt then becomes clinically hypothyroid for 6 to 12 weeks, requiring temporary levothyroxine therapy.

Question 16

Which are the painful thyroiditis?

Which are the painless thyroiditis?

Answer 16

Painful thyroiditis: are inflammatory (de Quervain or subacute granulomatous thyroiditis), infectious (suppurative), and radiation-induced

Painless thyroiditis: postpartum thyroiditis, silent thyroiditis, and drug-induced thyroiditis.

Question 17

How is treatment for painful thyroiditis? What are the different types?

Answer 17

*NSAIDs, systemic glucocorticoids, treat the thyrotoxicosis with BB and thiamine

• de Quervain-inflammatory
• subacute granulomatous
• Subacute–most common, caused by viral etiology, hx of viral illness preceding thyroiditis
• Radiation thyroiditis–occurs 5-10 days after treatment with radioactive iodine
• infectious thyroiditis: may be seen in an immunocompromised patient–staph and strep can cause it

Question 18

When does postpartum thyroiditis occur? What is diagnostic of it?

Answer 18

• Postpartum thyroiditis may occur up to 1 year after delivery;
• The presence of TPO antibodies is nearly universal, and the likelihood of subsequent permanent hypothyroidism is very high

Question 19

Describe how to diagnose and treat central hyperthyroidism?

Answer 19

TSH-secreting pituitary adenomas are extremely rare. In this condition, serum TSH is detectable or normal in the setting of an elevated T4 and/or T3 concentration. A dedicated pituitary MRI will demonstrate an adenoma. Treatment should focus on removal of the pituitary tumor; thyroid-targeted therapy is ineffective

Question 20

What is subclinical hyperthyroidism?

Answer 20

Subclinical hyperthyroidism is a laboratory-based diagnosis, defined as the presence of a suppressed TSH level with normal T3 and T4 levels.

Question 21

How is subclinical hyperthyroidism diagnosed?

Answer 21

• TSH level with normal T3 and T4 levels.
• In patients with subclinical hyperthyroidism, repeat assessment of thyroid function should be performed 6 to 12 weeks after the initial tests, as the values will normalize in up to 30% of patients.

Question 22

When do you treat subclinical hyperthyoidism?

Answer 22

Treatment for subclinical hyperthyroidism is recommended when the thyroid-stimulating hormone level is less than 0.1 μU/mL (0.1 mU/L).

Question 23

What is the most common cause of hypothyroidism?

Answer 23

The most frequent cause is Hashimoto thyroiditis, also known as chronic lymphocytic thyroiditis.

Question 24

What are the most common iatrogenic causes of hypothyroidism?

Answer 24

Iatrogenic causes include surgery, radioiodine therapy, and external beam radiation therapy to the neck.

Question 25

What medications cause hypothyroidism?

Answer 25

Hypothyroidism may also be medication induced; the most common causative agents include lithium, amiodarone, interferons, interleukin-2, and tyrosine kinase inhibitors.

Question 26

How is Hashimoto’s thyroiditis diagnosed?

Answer 26

An elevated serum TSH level indicates the diagnosis of primary hypothyroidism. In patients with an elevated TSH that is less than 10 μU/mL (10 mU/L), a low serum T4 measurement is helpful, as a frankly low value indicates that thyroid hormone replacement is necessary. The presence of TPO antibodies suggests that Hashimoto thyroiditis is the underlying cause. Thyroid imaging is not indicated unless there is concern for a nodule on physical examination.

Question 27

How is hypothyroidism treated?

Answer 27

In patients with a thyroid-stimulating hormone level greater than 10 μU/mL (10 mU/L), daily thyroid hormone replacement is recommended and should be taken on an empty stomach; the dose should be titrated based on thyroid-stimulating hormone levels measures 6 to 8 weeks after any dose change.

Question 28

What is subclinical hypothyroidism?

Answer 28

Subclinical hypothyroidism is defined as an elevated serum TSH level with a normal T4 level.

Question 29

How do you manage subclinical hypothyroidism?

Answer 29

In patients with suspected subclinical hypothyroidism, repeat measurement of the thyroid-stimulating hormone level is recommended, as it will normalize in up to 30% of patients by 6 weeks.

Question 30

What are the thyroid changes that occur in pregnancy?

Answer 30

Increased estrogen levels cause a rise in thyroxine-binding globulin. To maintain a stable free T4 and T3, thyroid hormone production is increased and TSH remains within the normal reference range for the patient’s trimester (see later discussion for trimester-specific ranges).

Question 31

What pregnant ladies is TSH screening indicated in?

Answer 31

TSH screening is indicated in women with:

• a risk of thyroid gland dysfunction, including those already on thyroid hormone replacement therapy
• those with autoimmune disorders
• goiter, previous head/neck irradiation
• previous thyroid surgery
• known positive TPO antibodies
• positive TSI antibodies
• strong family history of thyroid dysfunction
• those who live in iodine-deficient areas
• or those older than 30 years.

Question 32

For women already on levothyroxine, how much should you increase the dose when they get pregnant?

Answer 32

In patients on levothyroxine replacement, the dose of the medication may need to be increased, on average by 30% to 50%, and patients should have their TSH level checked as soon as a pregnancy test is positive.

Question 33

For women with hypothyroidism, how should it be monitored and managed through pregnancy?

Answer 33

TSH testing should be performed every 6 weeks throughout pregnancy, with adjustments in thyroid hormone replacement dosing as needed to maintain the TSH within the trimester-specific normal range. The largest dose escalations typically occur in the first trimester, with more dose stability later in pregnancy.

Question 34

What are the thyroid hormone levels for euthyroid sick sinus syndrome?

Answer 34

The typical pattern is initially a low T3 level, followed by a decline in the T4 level. As the patient becomes more critically ill, the TSH level may also decline, creating a clinical picture that is difficult to discern from central hypothyroidism. Rarely, TSH can be elevated in ESS.

Question 35

For someone with euthyroid SSS when should follow-up testing be performed?

Answer 35

After patients with euthyroid sick syndrome are discharged from the hospital, thyroid function abnormalities may persist for several weeks so follow-up thyroid function tests should not be repeated until 6 weeks after discharge.

Question 36

How is thyroid storm different from thyrotoxicosis?

Answer 36

Thyroid storm is a severe manifestation of thyrotoxicosis with life-threatening secondary systemic decompensation (shock). The cardinal features for diagnosis include elevated temperature, significant tachycardia, heart failure, gastrointestinal dysfunction (nausea, vomiting, diarrhea, and/or jaundice), and neurologic disturbances. The range of central nervous system manifestations includes increasing agitation, emotional lability, confusion, paranoia, psychosis, or coma. Although thyroid storm has been reported with many causes of thyrotoxicosis, it occurs most commonly with Graves disease. Thyroid storm may be precipitated by another event such as infection, surgery, myocardial infarction, trauma, or parturition. Administration of radioactive iodine therapy to a patient with untreated or uncontrolled hyperthyroidism can trigger thyroid storm.

Question 37

How is thyroid storm managed?

Answer 37

• Beta blocker: propranolol
• Thionamide: PTU
• these two block peripheral conversion of T4 to T3
• high dose glucocorticoids
• At least 1 hour after the first dose of a thionamide, iodine drops should be administered to inhibit further release of thyroid hormone from the gland.
• Acetaminophen and cooling blankets may be used to control the hyperthermia.

Question 38

Explain myxedema coma

Answer 38

Myxedema coma is an extreme but rare manifestation of hypothyroidism, resulting in life-threatening secondary systemic decompensation. Without a frankly low T4 level, myxedema coma is unlikely, regardless of the degree of TSH elevation.

Question 39

How is myxedema coma managed?

Answer 39

• If myxedema coma is suspected, the serum TSH and T4 levels should be tested immediately
• Diagnosis is made based on the clinical presentation and the coexisting metabolic abnormalities
• Check serum cortisol level to evaluate for concomitant adrenal insufficiency prior to initiation of thyroid hormone replacement
• Start high-dose glucocorticoid therapy
• glucocorticoid therapy may be discontinued if the serum cortisol level is found to be normal or high.

Question 40

If you notice a thyroid nodule on exam what do you do next?

Answer 40

All patients with a suspected thyroid nodule should have a neck ultrasound that includes evaluation of the thyroid and cervical lymph nodes.

Question 41

Workup of a patient with a thyroid nodule, incidental or otherwise… and if TSH is high or low

Answer 41

• TSH suppressed: Measure T3 and T4
• Consider radionuclide scan

*TSH high: the radionuclide scan is unnecessary as it is unlikely to reveal a hot nodule; the evaluation should proceed with an ultrasound and possible FNA.

Question 42

Nodule benign by FNA and stable on repeat imaging?

Answer 42

Nodules that are benign by FNA should be followed with repeat ultrasound examination in 6 to 18 months to assess for significant changes. If the nodule is stable on repeat imaging and lacks suspicious features, clinical examination and repeat ultrasound can be extended to longer intervals, such as 3 to 5 years.

Question 43

Nodule benign by FNA but changing on repeat imaging?

Answer 43

Nodules that are benign by FNA should be followed with repeat ultrasound examination in 6 to 18 months to assess for significant changes. Greater than 50% change in nodule volume or interval development of concerning ultrasound characteristics should prompt a repeat FNA to evaluate for a false-negative initial biopsy; however, according to the American Thyroid Association, thyroid nodules with two benign FNA cytology results do not require routine ultrasound surveillance because the risk of malignancy is almost zero.

Question 44

When is a hemithyroidectomy preferred?

Answer 44

Malignant nodules and those that are suspicious for malignancy require prompt excision; this is typically done with total thyroidectomy, but hemithyroidectomy may be preferable for patients younger than 45 years of age with a tumor smaller than 4 cm

Question 45

How do you manage a multinodular goiter?

Answer 45

Surgical removal of a large multinodular goiter is the treatment of choice if the compressive symptoms are significant, if malignancy is suspected, or if the patient desires cosmetic intervention.

Question 46

How do you work up a multi nodular goiter?

Answer 46

-extent of mass effect, additional testing and imaging, including noncontrast CT of the neck/chest, barium swallow, direct laryngoscopy, and/or spirometry with flow-volume loops

Question 47

What is something that occurs in elderly women with a history of Hashimoto’s thyroiditis? How is it treated or managed?

Answer 47

Primary thyroid lymphoma is a rare condition that typically occurs in elderly women with a history of Hashimoto thyroiditis

symptomatic, rapidly enlarging goiter with a very firm texture. Patients may also have systemic lymphoma symptoms and lateral cervical lymphadenopathy. The diagnosis can be made by FNA. Treatment typically involves chemotherapy and/or radiation therapy. Surgery generally is not indicated, but it can be used to aid in diagnosis when FNA is not informative.

Question 48

What is the treatment of well-differentiated thyroid cancer?

Answer 48

Treatment of well-differentiated thyroid cancer includes a combination of surgery, radioactive iodine, and levothyroxine suppression of thyroid-stimulating hormone for patients with persistent disease or high risk of recurrence.