Endocrine Flashcards
Who is more affected by thyroid disease?
Women 3x more
Active hormones produced by thyroid gland?
T3 and T4
Which thyroid hormone is more potent?
T3
Which is the major circulating hormone secreted by thyroid?
T4
What form is T3 and T4 mostly in?
Bound form and T4 is inactive by TBG thyroxine binding globulin
Half life of T4?
Slowly metabolized, long half life of 7 days
Half life of T3?
Greater potency and shorter half life of 1.5 days
Thyroid hormone acts directly on what 2 sites?
Cardiac myocytes (increase contractility) and vascular smooth muscle (vasodilates)
3 usual therapies for hyperthyroidism?
- Anti thyroid (methimazole or propulthiouracil (PTU))
- Iodide
- Beta blockers
How does methimazole or PTU work?
Inhibit organification and coupling steps in thyroid hormone synthesis (MIT, T3 and T4)
How long does it take methimazole and PTU to work?
6-8 weeks to achieve euthyroid status
How does iodide work?
Inhibits release of hormones; decreasing thyroid synthesis and release so reducing gland size and vascularity
When is iodide used?
Urgent uses because immediate onset but short lived
What is iodide pretreated with?
Antithyroid drugs to avoid exacerbation
How does BB propranolol work?
Decreases T4 to T3 conversion
Hyperthyroidism general anesthesia changes (2)
- Induction agent may be slower and require increased concentration of inhaled anesthetic due to increase CO
- Increased anesthetic requirements to control BP and HR
Hyperthyroidism is thought to have increased sensitivity to what?
Catecholamines (NE, Epi, ephedrine - indirect acting agent)
What is recommended to control BP for hyperthyroidism?
Direct acting non catecholamines like phenylephrine
How are hyperthyroidism pts respiratory muscles?
Weak so may need prolonged mechanical ventilation post op
Hyperthyroid pts undergoing surgery: (3)
- Euthyroid status in preop
- Elective surgery take up to 6-8 weeks
- Treat with antithyroid agents, BB, glucocorticoids
During surgery for hyperthyroidism, what is propranolol’s 2 jobs?
- Manage CV effects
2. Decrease peripheral T4 to T3 conversion
How much Propranolol should be give for hyperthyroidism during procedure?
10mg IV and titrate to HR <90
What else can you give during procedure for hyperthyroidism and why?
Dexamethasone
Decrease peripheral conversion of T4 to T3
Steps to occur to treat thyroid storm (8)
- Immediately administer BB
- Consult endocrinologist
- Propranolol 10 mg IV
- Dexamethasone 2mg IV or hydrocortisone 100-200mg
- Cooling blankets
- Acetaminophen
- Phenylephrine if vasopressor needed
- NG administration of antithyroid drug (PTU)
If symptom during or shortly after surgery in pt without known hyperthyroidism and before lab confirmation, how do you mange?
Manage like MH
Pts with chronic hypothyroidism are treated with what (3)
Thyroid replacement hormone:
- Levothyroxine (T4)
- L-triiodythyronine (T3)
- Liotirx (T4:T3 ratios)