All 'myx'ed up....

When discussing a case of hypothyroidism it important to consider the differential of hypothyroidism.....

Causes of Hypothyroidism:
Primary:

• Hashimotos
• RAI
• Surgery
• Subacute Thyroiditis
• Excess Iodine Intake
• Meds: lithium, amiodarone
• Iodine deficiency

Secondary Hypothyroidism (pituitary)
Tertiary Hypothyroidism (hypothalamus)
Peripheral Resistance to thyroid hormone

Investigations:

• TSH, FT3, FT4
• Anti-thyroid antibodies (anti-thyroglobulin, anti-TPO)
• Complications: CBC (normocytic anemia), lytes (hypoNa), fasting lipids, CK

Treatment:
L-thyroxine replacement (start at 25 - 50 mcg daily & increase slowly)
25 mcg daily for those with CAD, 50 mcg daily for elderly (age > 50)
full dose (usually 1-2mcg/kg daily) for young pt’s with no CAD
Titrate q 4wks based on TSH, FT4


Consider severity of hypothyroidism…..? myxedema coma:

Clinical Features:

-hypothermia
-hypotension / bradycardia
-hypercarbia
-hypoNa
-hypoGlu
-elevated CK

Management of this emergency……30-40%mortality!

• Admit to monitored setting
• Supportive
• Support ventilation as needed
• Monitor ABG’s
• Support BP with fluids / pressors
• Passive warming
• iv glucose for hypoglycemia – ± stress steroids, test for concomitant adrenal insufficiency
• Watch Na- likely SIADH

Specific:

• L-thyroxine iv bolus, followed by daily dosing (iv/PO)
• Adrenal insufficiency may be precipitated so hydrocortisone until plasma cortisol is known
  can have associated primary adrenal or secondary adrenal insufficiency
• Treat underlying cause (consider broad-spectrum Abx until cultures back)
• Refer to Endocrine