Block 4: Thyroid Disorders Flashcards
Who are more at risk for thyroid problems?
Women
Undiagnosed thyroid disease increases the risk of?
- CVD
- Osteoporosis
- Infertility
How is TH formed?
Active uptake pumps concentrate iodiDe
What TH has a shorter half-life and stronger affinity to receptors?
T3
TH ratio in a normal thyroid gland?
T4: 80%
T3: 20%
Difference between bound and unboud TH?
TH is higly bound, howeverer is not active. TH is only active in free form
How is TH regulated?
- Low T3 and T4 levels signal hypothalamus to release thyroid releasing hormone (TRH)
- TRH signals anterior pituitary to release thyroid stimulating hormone (TSH)
- TSH signals thyroid to release T3 and T4
- High levels of T3 and T4 decreases production of TRH and TSH by a negative feedback loop
- Disruption of any one of these regulator mechanisms can cause abnormal levels of T3 and T4 leading to thyroid disease
TFT values?
Whar is thyrotoxicosis?
Inappropriately high thyroid action when those tisses are exposed to to excessive levels of T4, T3, or both
Signs and sx of thyrotoxicosis?
- Fine hair
- Lid lag
- Weight loss with an increased appetite
What is hyperthyroidism and what are the types?
A form of thyrotoxicosis due to INCREASED synthesis and secretion of thyroid hormones by the thyroid and the overproduction of TH
1. Primary
2. Secondary
What is a common cause of hyperthyroidism?
Graves Dx
Whar are sx of Graves?
- HYPERthyroidism—results from action of thyroid-stimulating antibodies (TSAbs)
- Goiter
- Exophthalmos
- Pretibial myxedema
What is a goiter?
Swollen neck due to diffuse enlargement of the thyroid gland may require surgery
What is exophthalmos?
Graves’ ophthalmopathy: autoimmune related protruding eyeball
What is Pretibial myxedema?
Localized lesions and thickening of skin resulting from depositions of hyaluronic acid usually but not always on the pretibial area)
Tx for Graves?
antithyroid drugs (ATD), surgery, or radioactive iodiNe (RAI)
Tx for toxic multinodular goiters?
RAI or surgery
Tx of toxic agnoma?
RAI or surgery
Tx for postpartum thyroiditis?
Beta blockers (propranolol or metoprolol) may help with adrenergic symptoms
ATDs are NOT indicated. They do not decrease the release of preformed thyroid hormone
Pharm tx for hyperthyroidism?
Thioureas/Anti-thyroid Drugs (ATD)
1. Methimazole (Tapazole; MMI)
2. Propylthiouracil (PTU)
Nonpharm for hyperthyroidism?
- Surgery (Thyroidectomy)
- Irradiation with Radioactive iodiNe (RAI: sodium iodiNe 131I)
Adjunctive tx for hyperthyroidism?
- b-blockers
- IodiDe containing compounds
Initial tx for hyperthyroidism is dependent on…?
- Age
- Concurrent physiology
- Comorbidities
- Convenience
MOA of thioamides?
- Inhibits thyroid peroxidase enzyme (TPO)
- PTU inhibits the peripheral conversion of T4 to T3 (MMI does NOT have this effect)
Place is therapy for thioamides?
- Preferred treatment in children, adolescents, and pregnancy
- Useful in elderly patients, patients with a limited life expectancy, and patients with poor surgical risk
- Initial treatment in severe cases or to prepare for RAI or surgery
ADR of thioamides?
- Hepatotoxicity
- Agranulocytosis (more likely in PTU)
How do you monitor and maintain thioamides?
Sx diminish after 4-8 weeks and circulating TH levels return to normal:
1. Beta blockers may be used during this time to reduce adrenergic symptoms
2. After response, start tapering. Change doses monthly to allow endogenously produced T4 to reach a new steady state concentration
3. Therapy should continue for 12 to 24 months
4. If euthyroid after one year D/C ATD
5. If relapse occurs, RAI is preferred over a second course of ATD
Monitoring: TFTs every 4 weeks
What are the advantages and disadvantages of using thioamides?
Advantages:
1. Non invasive
2. Low cost
3. Low risk of permanent hypothyroidism
4. Possible remissionbs due to immune effects
Disadvantages:
1. Low cure rate
2. ADR
3. Drug compliance
MMI is a drug of choice for paitents with ATD except?
- Pregnancy (1st trimester) and lactation
- Thyroid storm
- Refuse RAI/surgery after a minor reaction to MMI
You would use PTU
When would PTU be a drug of choice?
Thyroid Storm, the 1st trimester of pregnancy and lactation
When should surgery be considered? When should it be avoided?
- Large goiters
- Severe Graves ophthalmopathy
- Lack of remission on ATD
- Graves
- 2nd trimester
- Refusal for RAI therapy
1st and 3rd trimester
Complications of surgery?
- Laryngeal nerve damage
- Hypothyroidism
How do you prepare for thyroidectomy?
- MMI until euthyroid
- Add iodides (500 mg/day) for 10 to 14 days prior to surgery to decrease vascularity of the gland and during the immediate post operative period
- Propranolol for several weeks before surgery and 7 to 10 days after surgery
Tx after surgery?
- MMI should be stopped at the time of the thyroidectomy
- Beta blockers should be tapered off after surgery
- L-thyroxine should be started at 1.6 mcg/kg daily
- TSH checked 6 to 8 weeks post-op
What are the advantages and disadvantages of surgery?
Advatnages:
1. Rapid, effective treatment, especially patients with large goiters
2. Useful when coexisting ssuspicioius nodule present
Disadvantages:
1. Most invasive
2. Least costly in long-term after quality of life adjustment
3. Permanent HYPOthyroidism
4. Pain
5. Scarring
Place in therapy for radioactive iodine 131?
- Permanent tx for hyper
- Best for toxic nodules and multinodular goiters