exam 3 thyroid disorders Flashcards
Thyroid Disorders
Hypothyroidism: underactive thyroid
Hyperthyroidism: overactive thyroid
Thyroid Function Tests
Laboratory Parameters
Serum TSH is the single best screening test for thyroid dysfunction
Serum Free T4 (FT4) is recommended to confirm suspicion of hypothalamic or pituitary disease
HYPOTHYROIDISM
Under-production of thyroid hormones
More common in females and incidence increases with age
Hypothyroidism causes
Hashimoto’s disease – most common
- Autoimmune condition in which a patient’s antibodies attack their own thyroid gland
Iodine deficiency
Surgical removal of part or all of the thyroid gland
Congenital hypothyroidism
Drugs: amiodarone, interferons, lithium, nitroprusside, tyrosine kinase inhibitors
Thyroid gland ablation with radioactive iodine (secondary hypothyroidism)
Pituitary failure (secondary hypothyroidism)
hypothyroidism complications
Cardiovascular disease
- Cardiomyopathy, heart failure, hyperlipidemia, coronary artery disease
Myxedema coma
- End stage of long-standing uncorrected hypothyroidism requiring IV thyroid hormone
Depression
Infertility
hypothyroidism signs and symptoms
Cold intolerance
Bradycardia
Weight gain
Weakness
Fatigue
Constipation
Coarse, thinning hair
Myalgias
Menorrhagia
Goiter
hypothyroidism lab values
↑ TSH (always collected) and ↓ FT4 (may or may not be collected)
↓ T4, ↓ T3 – not routinely measured
hypothyroidism treatment
other hypothyroidism treatments
Desiccated thyroid (Armour Thyroid ®): T3 and T4
- Discouraged since preparations can contain variable amounts
- Conversion of desiccated to levothyroxine: 1 grain (60-65 mg) = 100 mcg
Liotrix (Thyrolar ®): T3 and T4 in 1:4 ratio
- Also not recommended
Liothyronine (Cytomel ®, Triostat ®): T3
- Also not recommended
subclinical hypothyroidism
↑ TSH with normal FT4
Controversy if should treat with levothyroxine
- Likely to benefit: TSH > 10 mIU/L
- Consider treatment: TSH 5-10 mIU/L + symptoms
- Benefits clearest in younger populations
Generally lower dose compared to when treating hypothyroidism (e.g. levothyroxine 25-75 mcg/day)
hypothyroidism drug interactions
hypothyroidism monitoring
Observe clinical signs and symptoms
Check TSH levels (T4 rarely):
- Initially every 4 - 8 weeks until levels are normal or when change dose or preparation
- 6 months
- Yearly
Over-dosing in elderly patients leads to atrial fibrillation and fractures
- May need dose reduction as patient ages
hypothyroidism in pregnancy
Pregnant women with hypothyroidism may have children at risk of impairment in their intellectual function and motor skills, unless appropriately treated
Levothyroxine – pregnancy risk factor A
- Preferably initiated prior to pregnancy
- Will require 30-50% ↑ in dose throughout pregnancy course
- Mother will require ↑ dose for several months post-partum – monitored freqently
Upper limit of normal TSH goals
- 1st trimester – 2.5 mIU/L
- 2nd trimester – 3 mIU/L
- 3rd trimester – 3.5 mIU/L
hypothyroidism counseling
Take in the morning on an empty stomach ≥ 30 - 60 minutes before breakfast
- Increases absorption
Different brands of levothyroxine may not work the same
- If your new pills look different, ask the pharmacist
Tell your doctor if you become pregnant during treatment
- If you become pregnant, your dose will likely need to be increased
You may notice a slight reduction in symptoms within 1 to 2 weeks, but the full effects can take up to two months
Even if you feel better, continue taking this medication for the rest of your life
Your blood will need to be tested at least annually to make sure your dose is optimal
HYPERTHYROIDISM
Over-production of thyroid hormones
hyperthyroidism causes
Grave’s disease – most common cause
- Autoimmune disorder where the antibodies simulate the thyroid to produce too much T4
Toxic Multinodular Goiter
- Growth of multiple thyroid nodules that results in unregulated T3 and T4
Toxic Adenoma
- Growth of a single, usually benign thyroid nodule that produces unregulated T3 and T4
Thyroiditis
- Inflammation of the thyroid gland commonly due to a viral infection
Drugs: iodine, amiodarone, interferons, excessive doses of thyroid hormone
hyperthyroidism signs and symptoms
Heat intolerance
Goiter
Weight loss
Exophthalmos
Agitation
Diplopia
Anxiety
Fine, thinning hair
Palpitations
Tachycardia
Fatigue
Tremor
Muscle weakness
Irregular menses
Diarrhea
Insomnia
hyperthyroidism lab values
↓ TSH and ↑ FT4
↑ T4, ↑ T3 – not routinely measured
hyperthyroidism complications
Arrhythmias
Heart failure
Osteoporosis
hyperthyroidism symptom control
Beta blockers
- Reduce palpitations, tremors, and tachycardia
- However, does not correct underlying disorder (only treats the symptoms)
- May use any beta blocker, although propranolol and nadolol may block T4 to T3 conversion at high doses (not clinically significant) – this is an advantage
hyperthyroidism treatment
- Anti-thyroid medications, radioactive iodine (RAI-131), or surgery
- Anti-thyroid medications
- Thionamides – inhibit synthesis of thyroid hormones by blocking the oxidation of iodine in the thyroid gland (decrease levels of thyroid hormones)
- Additional mechanism of Propylthiouracil: inhibits peripheral conversion of T4 to T3
- Onset of action is not seen until stored hormone is depleted, which may take 4-8 weeks (monitor TSH)
- When clinical symptoms begin to diminish and thyroid function tests begin to decline, the dose is decreased to a maintenance dose (prevents hypothyroid state)
- Continued for 12-24 months until the patient is in remission – high relapse rate
- Thionamides – inhibit synthesis of thyroid hormones by blocking the oxidation of iodine in the thyroid gland (decrease levels of thyroid hormones)
anti-thyroid medications
RAI-131 – radioactive iodine
hyperthyroidism surgery
thyroid storm
drugs of choice
Case 1
S/sx: fatigue, constipation, Low T4, High TSH
Case 2
S/sx: weight loss, increased appetite, low TSH, high T4, increased HR, Temp
