97. Thyroid Flashcards
In patients with established thyroid disease, do not check thyroid-stimulating hormone levels too often, but rather test at the appropriate times, such as when ? (3)
- after changing medical doses.
- when following patients with mild disease before initiating treatment.
- periodically in stable patients receiving treatment.
When examining the thyroid gland, use proper technique. Explain how.
- from behind the patient, ask the patient to swallow)
- especially to find nodules (which may require further investigation).
Name Risk Factors for Thyroid Disease (6)
- Women >45yo
- Postpartum. No clear impact (benefit or harm) for universal screening in pregnancy
- Radiation
- Drug-induced (lithium, amiodarone)
- Autoimmune disease (eg. DM1)
- Strong family history of thyroid disease
Describe effect of lithium on thyroid (3)
- can cause goiter
- hypothyroidism (more common)
- hyperthyroidism
Describe effect on thyroid : Interferon alfa-2b (2)
may cause hypothyroidism or hyperthyroidism
Name sx : Hypothyroidism (8)
- Mood: Depression
- Memory
- Motor: Fatigue/Lethargy
- Mass: Weight gain
- Metabolism: Cold intolerance
- Menstrual irregularities
- Constipation
- Dry skin
Name sx : Hyperthyroidism (7)
- Palpitations/ tachycardia/ atrial fibrillation
- Widened pulse pressure
- Nervousness and tremor
- Heat intolerance
- Weight loss
- Muscular weakness
- Usually goiter is present
What to do if TSH high (> 4-5 mU/L) (2)
Possible Primary Hypothyroidism
* FT4 to determine degree of hypothyroidism
* Anti-TPO Ab once
What to do if TSH low (<0.2mU/L)
Possible Primary Hyperthyroidism
* Free T4 and T3 to determine degree of hyperthyroidism
* If no obvious cause (eg. Graves - new ophthalmopathy, goiter)
(1) Thyrotropin receptor antibodies (TRAb)
(2) Radioactive iodine uptake (contraindicated in pregnant/breastfeeding)
(3) Ultrasound with thyroidal blood flow
If abnormal thyroid size, nodules, what to do ?
- Thyroid ultrasound
- FNA for nodules >1cm or 5mm and suspicious features (r/o cancer)
Name DDX primary hypoT4 (7)
- Chronic autoimmune thyroiditis
- Iatrogenic
- Iodine deficiency/excess
- Drugs
- Infiltrative diseases
- Transient hypothyroidism
- Congenital thyroid disease
Name iatrogenic causes of hypoT4 (4)
- thyroidectomy
- radioiodine therapy
- external radiation
Name drugs that cause hypoT4 (7)
- thionamides
- lithium
- amiodarone
- interferon-alfa
- interleukin-2
- perchlorate
- tyrosine kinase inhibitors
Name Infiltrative diseases that cause hypoT4
- thyroïdite fibreuse
- hémochromatose
- sarcoïdose
*
Name : Transient hypothyroidism (4)
- Thyroïdite (lymphocytaire silencieuse, granulomateuse subaiguë, post-partum)
- Thyroïdectomie subtotale
- Thérapie à l’iode radioactif pour Graves
- Arrêt des doses suppressives d’hormones thyroïdiennes chez les patients euthyroïdiens
Name central hypoT4 causes (2)
- TSH deficiency
- TRH deficiency
Name types of HypoT4 (3)
- Primary
- Central
- Résistance généralisée aux hormones thyroïdiennes
Name ddx avec hyperT4 : Normal/high radioiodine uptake (4)
- Autoimmune
- Tissu thyroïdien autonome
- TSH-mediated
- Human chorionic gonadotropin
Name autoimmune hyperT4 ddx (2)
- Graves’ disease
- Hashitoxicosis
Name Autonomous thyroid tissue
hyperT4 ddx (2)
- Toxic adenoma
- Toxic multinodular goiter
Name Human chorionic gonadotropin
hyperT4 ddx (2)
- Hyperemesis gravidarum
- Trophoblastic
Name TSH-mediated
hyperT4 ddx (1)
Pituitary adenoma
Name Thyroiditis
hyperT4 ddx (5)
- Subacute granulomatous (de Quervain’s) thyroiditis
- Painless thyroiditis (silent, lymphocytic, postpartum)
- Amiodarone
- Radiation thyroiditis
- Palpation thyroiditis
Name ddx avec hyperT4 : Near absent radioiodine uptake (3)
- Thyroiditis
- Exogenous thyroid hormone intake (excessive replacement therapy)
- Ectopic hyperthyroidism
Name Ectopic hyperthyroidism
hyperT4 ddx (2)
- Struma ovarii
- Metastatic follicular thyroid cancer
Name causes : Subclinical hypothyroidism (5)
- possible CAD
- heart failure
- stroke
- lipids
- infertility
Describe tx : Subclinical hypothyroidism (2)
- Consider treatment if TSH≥20mU/L, symptomatic, or risk (elevated Anti-TPO Ab, Goiter, strong family history of autoimmune, pregnancy)
- Consider treatment in infertility
Name risks : Subclinical hyperthyroidism
- atrial fibrillation/flutter
- heart failure
- lower Bone Mineral Density
Desribe tx : Subclinical hyperthyroidism
Consider treatment if TSH <0.1 mIU/L and
* Symptomatic (palpitations, tremor, nervousness)
* >65yo
* Comorbidities such as heart disease or osteoporosis
* Postmenopausal (<65yo) and not taking estrogen/bisphosphonates
Describe tx : Subacute granulomatous thyroiditis (viral infection, painful thyroid) (1)
NSAIDs
Treatment of Hypothyroidism (5)
- Levothyroxine treatment of choice, start 12.5-50mcg/day
- Target TSH euthyroid range (except in secondary hypothyroidism, where target FT4)
- No evidence for levothyroxine in euthyroid (except in thyroid cancer target undetectable TSH to reduce recurrence by 40%)
- Avoid TSH <0.1mIU/L
- Consider higher serum TSH target in elderly and hospitalized (eg. 8)
Describe follow-up tx hypoT4 (4)
- Repeat TSH q3-4 months until stable, then yearly
- If dose higher than expected, evaluate for GI disorder (H pylori gastritis, atrophic gastritis, celiac)
- Follow serum TSH when started on medications, change in body weight, aging, pregnancy
- Poor adherence, weekly levothyroxine should be considered
Describe tx : Myxedema coma (7)
- Altered mental status
- hypoventilation
- hypothermia
- hypotension
- bradycardia
- hypoNa
- hypoglycemia
Describe tx : Myxedema coma (4)
- Levothyroxine (T4) loading dose 200-400mcg IV, then 1.6mcg/kg/day IV
- Liothyronine (T3) 5-20mcg followed by 2.5-10mcg q8h given with T4
- Glucocorticoids (hydrocortisone 100mg IV q8-12h x2d) until coexisting adrenal insufficiency can be excluded
- Supportive measures (ventilation, fluids, correction of hyponatremia and hypothermia)
What to do if elevated TSH vs low TSH ?
- Elevated TSH, rule out pituitary gland tumour
- Low TSH, consider radioiodine uptake scan
Describe tx : Graves (3)
- Thionamides (Methimazole - MMI or Propylthiouracil - PTU)
- Beta-blockers (for symptom control) : Atenolol 25-50mg daily (up to 200mg) until goal HR<90
- Ophthalmopathy: Steroids, radiation, surgical decompression
Describe tx : Thyroiditis (3)
- NSAIDs
- Steroids
- Beta-blockers for symptomatic treatment
Describe tx : Toxic adenoma/multinodular goiter (2)
- First-line: Radioiodine or surgery. May consider thionamide initially for short-term
- Beta-blockers for symptomatic treatment
Name sx : Thyroid storm (6)
- Hyperthermia
- Tachycardia
- N/V/D
- Dehydration
- Delirium
- Coma
Name causes : Thyroid storm (3)
- Trauma
- Surgery
- Radioactive Iodine
Describe tx : Thyroid storm (5)
- B-Blockers (Propranolol 60-80mg q4-6h)
- PTU 200mg PO q4h
- Iodine solution (delayed 1h after PTU)
- Iodinated radiocontrast
- High-dose IV hydrocortisone 100mg IV q8h
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