12: Thyroid gland

Question 0

Selenium

Answer 0

Dietary Selenium is essential for T3 production in cells

Question 1

Pemberton’s sign

Answer 1

• Intrathoracic goiter causing obstruction of SVC
• Distension of the left external jugular vein, facial erythema, and cutaneous varicosities as thoracic inlet rises
• May cause thoracic duct obstruction and chylothorax

Question 2

Effects of thyroid hormones- Body’s accelerator

Answer 2

• Increase rate of protein synthesis and degradation, as well as gluconeogenesis
• Increase CO, HR, Ventilation rate, Basal metabolic rate, body temp
• Potentiate effects of Catecholamines
• Potentiate brain development
• Thicken endometrium in females
• Increase metabolism of proteins and carbohydrates
• Regulate long bone growth by synergy with GH

Question 3

TSH- test

Answer 3

• Initial test of choice for thyroid disease

- Normal test excludes hyperthyroidism and 1 hypothyroidism

Question 4

Free T4(unbound) and Free T3- test

Answer 4

Thyroxine- binding glubulin (TBG): increased
-Pregnancy
-Estrogen therapy
-Oral contraceptives
-Acute phase of infectious hepatitis
-Tamoxifen
TBG: decreased
-Anabolic steroids
-Corticosteroids
-Nephrotic syndrome
Phenytoin + Aspirin displace T4 from TBG*

Question 5

Thyroglobulin (Tg)- test

Answer 5

Tg is used by thyroid gland to produce T4 and T3

-Tumor marker for Papillary or Follicular cancer

Question 6

Thyroid antibodies

Answer 6

Thyroid Peroxidase (TPOAb)
Thyroglobulin (TgAb)
-Hashimotos: TPOAb (100%)
-Graves: TPOAb (80%)
-TSI (Thyroid stimulating immunoglobulins): neonatal thyrotoxicosis caused by high materal TSI in 3rd trimester

Question 7

Radioactive iodine uptake (RAUI): high

Answer 7

• Graves disease
• Toxic single nodular goiter
• Toxic MNG
• Toxic thyroid adenoma
• Hashitoxicosis
• Choriocarcinoma
• Hydatiform mole
• TSH producing tumors

Question 8

Radioactive iodine uptake: RAUI: low

Answer 8

• Subacute thyroiditis
• Struma ovarii
• Excessive L thyroxine ingestion

Question 9

TFT: Normal

Answer 9

TSH: normal
FT4: normal
Dx: Euthyroid

Question 10

TFT: Hypothyroid

Answer 10

TSH: increased
FT4: decreased
Dx: primary hypothyroidism

TSH: low or normal
FT4: low
Dx: secondary hypothyroidism

TSH: incresed
FT4: normal
Dx: Borderline/Subclinical hypothyroidism

Question 11

TFT: Hyperthyroidism

Answer 11

TSH: decresed
FT4: normal
T3: normal
Dx: subclinical hyperthyroidism

TSH: decreased
FT4: normal
T3: increased
Dx: T3 toxicosis

TSH: decreased
FT4: increased
Dx: primary hyperthyroidism

Question 12

Euthyroid sick syndrome

Answer 12

TFT
-decreased T3 
-increased rT3 (decreased clearance)
-N or decreased FT4
-variable TSH 
Low T3 or T4: poor prognosis

Question 13

“NO SPECS” Grave’s disease classifications

Answer 13

0: No signs or sx
1: Only signs (lid retraction or lag), no sx
2: Soft tissue involvement (periorbital edema)
3: Proptosis (22mm)
4: Extraocular muscle involvement (diplopia)
5: Corneal involvement
6: Sight loss

Question 14

Diamond’s triad: Graves sx

Answer 14

Thyroid acropathy
-finger clubbing + periosteal new bone formation
Ophthalopathy
-Exophthalmos, lid lag, lid retraction, photophobia, periorbital edema, chemosis, diplopia
Infiltrative dermopathy
-Pre-tibial myxedema

Question 15

Rx: anti-thyroid meds for Hyperthyroidism

Answer 15

Carbimazole
Methimazole
Proppylthiouracil (can be used for pregnant + breastfeeding)
-Gradual regime: elderly (CHF)
Ineffective against
-Thyroiditis
-Toxic nodular goiter
-Toxic adenoma

Question 16

Rx: Radio-iodine

Answer 16

-Graves disease
-Toxic nodular goiter
-Toxic adenoma
Avoid pregnancy for four months after rx
Contraindication
-Graves ophthalmopathy*

Question 17

Rx: Iodine

Answer 17

Potassium iodide solution
Sodium ipodate
Iopanoic acid
-Thyroid storm
-Hyperthyroid pts undergoing non-thyroid surgical rx (with Propranolol)
-decreased vascularity of thyroid-> preoperative preparation of hyperthyroid pts undergoing subtotal thyroidectomy

Question 18

Rx: anti-adrenergic meds

Answer 18

Propranolol- inhibits extrathyroidal conversion of T4-> T3
Calcium channel blockers
-mild transient hyperthyroidism

Question 19

Surgical rx for hyperthyroidism

Answer 19

• Bring pt to euthyroid state prior to surgery to avoid thyrotoxic crisis
• Subtotal thyroidectomy is surgical method of choice
• Atenolol is started 1-2 weeks before surgery and given for 5-7 days post-op

Question 20

Thyroid storm- malignant hyperthyroidism- precipitating factors

Answer 20

• surgery
• infection+sepsis
• trauma
• DKA
• pregnancy+eclampsia

Question 21

Thyroid nodule- dx

Answer 21

Thyroid US- ddx solid from cystic nodules
Fine needle biopsy- indicated if nodule is solid and cold
CT head+neck- evaluate for metastatic disease

Question 22

Autoimmune thyroiditis: Rx

Answer 22

L- thyroxine: DO NOT treat too quickly because of CV risk

Question 23

Thyroiditis- cc

Answer 23

Acute: bacterial, fungal, radiation induced, Amiodarone
Subacute: viral (de Quervains), post partum, mycobacterial
Chronic: autoimmune (Hashimotos, Reidels)

Question 24

de Quervain thyroiditis- stages

Answer 24

1: hyperthyroid
2: euthyroid
3: hypothyroid
4: euthyroid

Rx: for hyperthyroid: beta blocker

Question 25

Riedels thyroiditis

Answer 25

Open Bx to exclude malignancy

Rx: surgery +/- Tamoxifen

Question 26

Rx: Carcinoma of Thyroid

Answer 26

Small: lobectomy + Isthmectomy
Large (>1.5cm): total or near-total thyroidectomy
-Radio Iodine administered to eliminate normal thyroid tissue and residual tumor cells
-TSH suppressive doses of L-thyroxine