Thyroid Disorders Lecture

Question 1

TSH turns thyroid ON/OFF by binding to receptors on…

Answer 1

Follicular cells

Question 2

Essential for making thyroid hormones

need 0.2 mg daily dietary intake

Answer 2

Iodine

Question 3

MIT + DIT + TG = ?

Answer 3

T3 (Triiodothyronine)

Question 4

DIT + DIT + TG =?

Answer 4

T4 (Thyroxine)

Question 5

The thyroid makes 13x more of which thyroid hormone?

Answer 5

13x more T4 than T3

Question 6

Which is more biologically active…T4 or T3?

Answer 6

T3

Question 7

50% of released T4 is deiodinated for form..

Answer 7

T3

Question 8

T4: only 0.025% free

T3: only 0.3% free

..what does this mean?

Answer 8

T3 is more biologically active!

only free hormone enters the cells and exhibits biologic activity

Question 9

Only ______ (FREE or BOUND) hormone enters cells and exhibits biologic activity?

Answer 9

Free!

Question 10

T4 conversion to T3 occurs in…

Answer 10

peripheral tissue

*especially liver, brain, heart

Question 11

Deiodinase enzymes do what?

Answer 11

Convert T4 to T3 (in peripheral tissue)

Question 12

• *Made in liver**
• *Binds 80% of thyroid hormone**; remainder binds to TBPA and albumin

Answer 12

Thyroxine Binding Globulin (TBG)

Question 13

Will changes in TBG, which ultimately cause changes in T4 and T4, cause clinical disease?

Answer 13

NO!

ie..TBG increases with estrogen (OCPs and pregnancy)

Question 14

Bind nuclear receptors in most tissues (brain, muscle, heart, kidneys, liver, pituitary)

Cell differentiation during development (cell growth, maturation, gene expression)

Help maintain thermogenic and metabolic homeostasis
Essential for normal metabolism, protein synthesis, organ function

Answer 14

Thyroid hormone actions

Question 15

MC thyroid disorders are result of…

Answer 15

Autoimmune proesses

(over/under stimulate thyroid hormone)

Question 16

Most informative lab tests when evaluating thyroid function?

Answer 16

TSH and T4

Question 17

Extremely sensitive indicator of thyroid function

Secretion controlled via negative feedback from thyroid hormone

norm= 0.27-4.2

Answer 17

TSH

Question 18

Asymptomatic patients with TSH levels 3-6 should be followed for development of…

Answer 18

Hypothyroidism

Question 19

Does a normal TSH exclude hyper/hypo thyroidism?

Answer 19

Majority of time YES!

Question 20

TSH is low
Free T4 is normal
Pt clinically seems to have hyperthyroidism

..what lab now?

Answer 20

T3!

(this is pretty much the only scenario you would check T3 levels)

Question 21

Anti-thyroid antibodies are elevated in…

Answer 21

Hashimoto’s thyroiditis
Graves disease

Question 22

TSH-R AB (TSAb)- thyroid stimulating hormone receptor antibodies (IgG) that stimulate….

Answer 22

gland activity

Question 23

TSH-R AB (aka TSI, thyroid stimulating immunoglobulin) are elevated in 80% of these patients?

Answer 23

Grave’s disease

(these stimulate gland activity)

Question 24

Definitive test for evaluating thyroid nodules

Answer 24

Fine needle aspiration

Question 25

This drug initially causes an increase in T4 (**hyperthyroidism**) but then resistance of T4 develops (**hypothyroidism**)

Answer 25

Amiodarone

Question 26

Causes: * *Autoimmune** (Hashimoto's Thyroiditis) * *Iatrogenic** (post radioactive iodine tx) * *Congenital** (1/4000 newborns) * *Drug induced** (Amiodarone) * *Secondary forms** (hypothalamic or pituitary dz)

Answer 26

Hypothyroidism

Question 27

Symptoms vary in severity Goiter often present 4/1000 women, 1/1000 men annually ## Footnote **lymphocytic infiltration of gland early presentation may be hyerthyroidism (release of stored hormone), BUT END RESULT IS HYPOTHYROIDISM**

Answer 27

Autoimmune hypothyroidism (ie Hashimoto's Thyroiditis)

Question 28

TPO and Tg antibodies present, often high titers Diffusely enlarged, firm, finely nodular thyroid

Answer 28

Autoimmune hypothyroidism

Question 29

Fatigue, lethargy Weakness, arthralgias Cold intolerance Constipation Dry skin, hair loss Headaches Menorrhagia **early or late symptoms of HYPOthyroidism?**

Answer 29

Early

Question 30

Slow speech Altered mentation Muscle cramps Hoarse voice Weight gain Amenorrhea **Early or late symptoms of HYPOthyroidism?**

Answer 30

Late

Question 31

Thin, brittle nails Thin, dry hair Delayed reflexes ..early or late sign of hypothyroidism

Answer 31

Early

Question 32

Goiter Facial/eyelid puffiness Alopecia Bradycardia Myxedema (non pitting edema) Pleural/pericardial effusion ..early or late signs of hypothyroidism?

Answer 32

Late

Question 33

Clinical syndrome associated with excessive levels of thyroid hormone

Answer 33

Thyrotoxicosis

Question 34

MC cause of **hyper**thyroidism

Answer 34

Grave's disease

Question 35

Causes: Toxic/"hot" adenomas/nodules Early Hashimotos or subacute thyroiditis Factitious- excessive thyroid hormone intake TSH secreting adenoma Amiodarone

Answer 35

Hyperthyroidism

Question 36

Does **amiodarone** cause hyper or hypo thyroidism?

Answer 36

can cause both

Question 37

**Antibodies directed to TSH receptor** Over active gland, which leads to: **hypersecretion, hypertrophy, hyperplasia** \*\*Goiters common! 8x more common in women onset 20-40 yo

Answer 37

Graves disease

Question 38

Hyperactivity, irritability, restlessness, anxiety Sweating, heat intolerance Palpitations Fatigue, weakness Decreased appetite, weight loss Diarrhea Decreased libido, oligomenorrhea

Answer 38

Symptoms of Graves disease (**hyperthyroidism**)

Question 39

Tachycardia Arrhythmias Fine tremor Goiter/bruit Warm/moist skin Oily, fine hair Proximal muscle weakness **Opthalmopathy** **Dermopathy** Hyperreflexia

Answer 39

Signs of Graves dz (**hyperthyroidism**)

Question 40

Opthalmopathy and dermopathy are unique to...

Answer 40

Graves disease

Question 41

proptosis/exophthalmos, "lid lag" occurs because of **lymphocytic infiltration of orbit, muscles, eyelids** \*may cause diplopia and compression of optic nerve

Answer 41

Opthalmopathy in **graves disease**

Question 42

Occurs in 3% Non inflammatory induration and plaque formation of pre-tibial areas leading to edema, thickened skin and "orange skinned" apperance (myxedema)

Answer 42

Dermopathy in **graves disease**

Question 43

**Cardiac arrhythmias** (STs, PACs, PVCs, new A fib) **High output cardiac failure** **Thyroid storm and crises:** extreme thyrotoxicosis with delerium, high fever, dehydration, death

Answer 43

Complications of Graves/hyperthyroidism

Question 44

``` Tx: Refer to endocrinology! Propranolol Thiourea drugs (ie Methimazole) ```

Answer 44

Tx for Graves/hyperthyroidism

Question 45

**Methimazole** works by inhibiting thyroid peroxidase and blocking organification of...

Answer 45

iodine! (used in tx of graves dz/hyperthyroid)

Question 46

Used to treat hyperthyroidism SE of pruritus Must monitor T4 levels Tx for 12-18 months **recurrent thyrotoxicosis in 50% after drug D/C'd**

Answer 46

Thiourea drugs

Question 47

First line thiourea drug for hyperthyroidism?

Answer 47

Methimazole (if pregnant or cant tolerate, use PTU)

Question 48

Definitive therapy for hyperthyroidism ## Footnote **tx of choice for Graves dz!!**

Answer 48

Radioactive iodine (I-131) \*but not during pregnancy!

Question 49

What will a pt develop within 1 year of radioactive iodine tx?

Answer 49

HYPOthyroidism ## Footnote **will need thyroid replacement for life**

Question 50

Opthalmopathy may WORSEN after tx, especially in....

Answer 50

smokers **can tx with prednisone, 2/3 will improve with prednisone**

Question 51

Is thyroid surgery the first line treatment for Graves?

Answer 51

No..not anymore \*only used now in kids and pregnant women with graves

Question 52

If a pt with Graves failed radioactive iodine treatment..now what?

Answer 52

Can remove thyroid gland (but preserve parathyroid glands)

Question 53

Do cardiac, ocular and psych problems always go away with treatment of Graves?

Answer 53

NO

Question 54

If single..usually benign adenoma or colloid cyst

Answer 54

Thyroid nodule (can be cancer even if single tho, must do fine needle aspiration)

Question 55

How do you rule out thyroid cancer if you feel a nodule?

Answer 55

Fine needle aspiration

Question 56

Tx of nodules

Answer 56

Can tx with radioactive iodine (some nodules may hypersecrete thyroid hormone so you want to tx)

Question 57

3x more common in women Well differentiated, slow growing **76% papillary 16% follicular** at risk if prior history of head/heck radiation

Answer 57

Thyroid cancer

Question 58

Dx: fine needle aspiration, ultrasound Tx: thyroidectomy with preservation of parathyroid glands

Answer 58

Thyroid cancer

Question 59

MC thyroid disease in the US 6x more common in females. can be familial **thyroid is diffusely enlarged with firm, small nodules**

Answer 59

Hashimoto thyroiditis

Question 60

MC type of thyroid cancer

Answer 60

Papillary (least aggressive and spreads by local extension)

Question 61

Diffuse uptake of radioactive iodine Graves Dz or Toxic nodule?

Answer 61

Graves! **toxic nodule has high uptake by nodule, none by rest of gland**

Question 62

TPO and Tg antibodies

Answer 62

Hashimoto's thyroiditis (autoimmune hypothyroidism)

Question 63

TSH-R Ab (TSAb)- IgG antibodies

Answer 63

Graves Dz