Thyroid

Question 1

Pathophysiology of the Thyroid

Answer 1

1) TRH is released from the hypothalamus and stimulates the release of TSH from the pituitary gland.
2) TSH stimulates the release of thyroxine (T4) and triiodothyronine (T3) from the thyroid gland.
3) T4 is converted to T3 in the periphery.

Question 2

What is HYPOthyroidism?

Answer 2

1) Low free T4
2) High TSH

Presentation: Descreased metabolism

Causes: Hashimoto’s Disease (Autoimmune disease which destroys the thyroid gland), Iodine deficiency, drugs

Symptoms: Cold intolerance, dry skin, fatigue, constipation, weight gain, voice changes, weakness, depression

Myxedema Coma: life-threatening emergency

Question 3

What is Hyperthyroidism?

Answer 3

1) High free T4
2) Low TSH

Question 4

Key drugs which causes HYPOthyroidism

Answer 4

1) Interferons
2) Amiodarone
3) Lithium
4) Carbamazepine
5) Phenytoin

Question 5

Monitoring

Answer 5

TSH is primarily tested

-Monitor every 4-6 weeks until normal, then
-4-6 months later, then
-Yearly

Question 6

Treatment of HYPOthyroidism

Answer 6

DOC: Levothyroxine (T4)

-Drug MUST be given consistently
-Take 60 mins before breakfast (with water)
-Dosing: 1.6 mcg/kg/day (IBW)

IV:PO (0.75:1) <—IV is 75% of PO dose

Question 7

HYPERthyroidism

Answer 7

Presentation: Increased Metabolism (“speeding up”)

Causes: Graves’ disease (autoimmune - antibodies stimulate the thyroid to increase T4)

Signs/Symptoms: Heat intolerance/sweating, agitation, tachycardia, diarrhea, weight loss, tremor, thinning hair

Question 8

Treatment of HYPERthyroidism

Answer 8

1) Radioactive Iodine
2) Thyroidectomy
3) Drugs
-Propylthiouracil (PTU)
-Methimazole (preferred, since PTU has liver toxicity)
-Beta blockers to control symptoms
-Temporary effect from potassium iodide (Lugol’s solution) or saturated solution of potassium iodide (SSKI)

Question 9

How to limit the risk of cancer after Radioactive Iodine?

Answer 9

Potassium Iodide treatment:
-Blocks accumulation of radioactive iodine in the thyroid gland
-Prevents thyroid cancer
-Take as soon as possible after exposure

Question 10

What is Thyroid Storm?

Answer 10

This is the life threatening emergency in HYPERthyroidism.

Signs/Symptoms: Fever, tachycardia, tachypnea, dehydration, profuse sweating, agitation, delirium, psychosis, coma

Treatment:
-PTU + Iodide (SSKI or Lugol’s) + beta blocker + dexamethasone

Question 11

Thyroid Disease in Pregnancy

Answer 11

HYPOthyroidism:
-Levothyroxine is still DOC
-30-50% increase in dose is usually needed

HYPERthyroidism:
-Postpone pregnancy until euthyroid (if able)
-In mild disease, treatment may be stopped
-If tx needed, PTU preferred in 1st trimester