Endocrine #2 (Thyroid Disorders) Flashcards by Tyler Cichowski

Explain the hypothalamus-pituitary-thyroid axis.

Describe a primary thyroid disorder. How about a secondary disorder?

Hypothalamus secretes TRH –> Pituitary secretes TSH –> Thyroid secretes T3 and T4

Primary: Disease in the thyroid

secondary: Disease in hypothalamus or pituitary

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MCC of Hyperthyroidism. Explain the pathophysiology of this.

Graves Disease

Autoimmune disease: TSH receptor antibodies target and stimulate TSH receptor leading to thyroid gland enlargement and hyperthyroidism (t3 and T4 production)

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Symptoms of hyperthyroidism

-Palpitations
-Heat Intolerance
-Tremors, weight gain
-Atrial fibrillation
-Ophthalmopathy: proptosis, exophthalmos, lid lag, diplopia, vision changes
-Pretibial Myxedema: swollen red patches on legs with non-pitting edema
-Warm, moist skin
-Fine Hair
-Diffusely enlarged non-tender goiter
-Hyperreflexia
-Insomnia
-Diarrhea
-Fine Tremors, Anxiety, Nervousness

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What labs are done for hyperthyroidism? What is specific for Graves Disease?

What is shown on radioactive iodine uptake scan?

-Decreased TSH + Increased Free T4 and T3

- Thyroid Stimulating Immunoglobulins (TSH receptor antibodies) for Graves

-Diffuse, increased iodine uptake (active and hyper)

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Treatment for Hyperthyroidism

_____ for Symptoms

______first line for thyroid hormone synthesis

______ for ophthalmopathy

Beta Blockers for symptoms

Methimazole or Propylthiouracil (PTU)

Glucocorticoids

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What treatment is preferred in the first trimester and for thyroid storm?

PTU

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What is thyroid storm/thyrotoxicosis?

Potentially fatal if untreated, thyrotoxicosis after a precipitating event (surgery, trauma, infection, pregnancy, preeclampsia)

-Hyperthyroid with an event that makes it much worse

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Symptoms of thyroid storm

-Hyperthyroid storm + CV Dysfunction (palpitations, tachycardia, A-fib, CHF)
-High fever, Tremors
-CNS Dysfunction: delirium, psychosis, stupor, coma

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Management for thyroid storm

-IVF + Propanolol + IV Glucocorticoids + PTU

-Then oral or IV sodium iodide

-Cooling blankets

-Antipyretics (not Aspirin)

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What is the MCC of Hypothyroidism in the US?

What is the pathophysiology of this?

Hashimoto Thyroiditis

Autoimmune thyroid cell destruction by anti-thyroid peroxidase and anti-thyroglobulin

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What are other etiologies of hypothyroidism?

What is the MCC in the WORLD?

Amiodarone, Lithium, Alpha-Interferon

Hashimoto’s

Iodine Deficiency MCC in world

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Symptoms of hypothyroidism

-Decreased metabolic rate
-Cold intolerance
-Weight gain
-Dry, thick rough skin
-Loss of outer 1/3 of eyebrow
-Nonpitting edema (Myxedema)
-Fatigue, memory loss, depression
-Constipation
-Anorexia
-Bradycardia
-Galactorrhea (increased prolactin)

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What is the normal lab values for hypothyroidism?

What is specific to Hashimoto?

What is seen on radioactive iodine uptake scan?

Increased TSH + Decreased free T3/T4

+ Antithyroid peroxidase and/or anti-thyroglobulin antibodies

Decreased iodine uptake (inactive and slow)

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Treatment for hypothyroidism

-Levothyroxine (Synthetic T4)

AKA Synthroid

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Explain what myxedema coma is.

Who should you think about when thinking about this condition?

What are some other “precipitating events”

Extreme form of hypothyroidism with a high mortality rate

Elderly women with a long-standing history of hypothyroidism in the winter

Discontinuation of Levothyroxine, infection, CHF, etc.

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Symptoms of Myxedema Coma

-Severe signs of hypothyroidism + bradycardia + hypothermia + hypotension + hypoglycemia + hyponatremia

Treatment for Myxedema Coma

-IV Levothyroxine + Supportive (ICU, passive warming), IV Glucocorticoids

What are some etiologies of iatrogenic hypothyroidism?

-Surgery without subsequent thyroid hormone replacement
-Amiodarone
-Lithium
-Alpha-Interferon

What is Cretinism?

What is the MCC in developing counties?

What is the MCC in developed countries?

Untreated congenital hypothyroidism

-Developing: lack of maternal iodine intake

-Developed: Dysgenesis of thyroid gland

Symptoms of cretinism

-Mental developmental delays
-Symptoms of hypothyroidism
-Goiter symptoms: hoarseness and dyspnea
-Coarse facial features: Macroglossia, umbilical hernia, hypotonia, feeding problems, prolonged jaundice

Treatment for Cretinism

Levothyroxine

What is subclinical hypothyroidism?

Isolated increased TSH in patients with little or no symptoms

What do labs show for subclinical hypothyroidism?

what is the treatment?

Isolated increased TSH + Normal T3/T4

Levothyroxine if TSH 10 or higher to prevent cardiovascular problems

Euthyroid Sick Syndrome is …..

It is MC seen in those with …..

Abnormal thyroid function tests in patients with normal thyroid function

Sepsis, malignancies, etc.

What unique thing is seen on diagnostics for Euthyroid Sick Syndrome?

Low T3 Syndrome: decreased free T3 and increased reverse T3 (inactive form of T3)

Risk factors for a thyroid nodule

-Extremes of age (very young or > 60) -History of head and neck radiation

What is the MC type of thyroid nodule?

-Follicular adenoma (colloid)

Although most thyroid nodules are asymptomatic, what symptoms CAN the patient have?

-Compressive symptoms: swallowing or breathing difficulty, neck/jaw/ear pain, hoarseness (recurrent laryngeal nerve impingement)

What nerve can be compressed by a thyroid nodule?

Recurrent laryngeal nerve

On physical exam, explain what a benign thyroid nodule feels/appears like? How about a malignant nodule?

Benign: varied, smooth, firm, irregular, sharply outlined, discrete, painless Malignant: rapid growth, fixed in place, no movement with swallowing, hypoechoic on US

What is the initial test done to evaluate the nodule?

-Thyroid function testing

If TSH is normal, what is indicated to further evaluate the nodule?

FNA with biopsy

What test is done after thyroid function tests to determine if a FNA is needed?

Thyroid US

A FNA with biopsy is performed on a thyroid nodule if it is > _____________________ or in highly suspicious nodules

if > 1.5 cm with normal TSH

What can be performed if the FNA is indeterminate or low or subnormal TSH? What results can you get with this and what does it mean?

Radioactive iodine uptake scan Cold nodules (no or low iodine uptake) should be biopsied to rule out malignancy Functioning (normal) or hot nodules have low malignancy potential

What is the treatment for a cold nodule, if thyroid cancer suspected, or an indeterminate FNA?

Surgical excision

If surgery is NOT performed for a thyroid nodule, when should you get an US?

Observation + follow up US every 6-12 months to observe for growth or changes