Thyroid Flashcards
Increased uptake RAI
- Hyperthyroidism due to Graves, multinodular goiter or thyroid adenoma
- Goitre
- Early-stage of Hashimoto thyroiditis
- Iodine deficiency
- TSH-producing adenoma
- The recovery phase from subacute, silent, or postpartum thyroiditis
- Pregnancy
- Lithium carbonate therapy
- Withdrawal of antithyroid medication
- Rebound after the suppression of thyrotropin
- Congenital defects of thyroid hormone synthesis
- Thyroid cancer (papillary or follicular)
- Trophoblastic disease
- TH resistance
Decreased uptake RAI
- Primary hypothyroidism (for example in congenital hypothyroidism)
- Central hypothyroidism
- Destructive thyroiditis
–Subacute thyroiditis
–Silent thyroiditis
–Postpartum thyroiditis
–Palpation thyroiditis
-Excess iodine
-Dietary supplements
-Radiological contrast
-Medications
–Amiodarone
–Antithyroid drugs
–Perchlorate
–Thiocyanate
–Sulphonamides
–Sulphonylurea
–High-dose glucocorticosteroids
–Topical iodine
-Post-thyroidectomy
-External neck radiation
-Thyroid cancer (nodule more likely to be malignant if “cold” nodule) - Struma Ovarriii
Teratogenic effects of MMI
- cutis aplasia (classic)
- choanal aresia
- esophageal atresia
- omphalocele
- VSD
Reasons for false negative CH NBS
- Central hypothyroidism
- Prematurity (may have delayed TSH increase)
- Low birth weight
- Monozygotic twin (mixing of fetal blood)
- Dopamine therapy (rapidly decreases TSH release)
- Acute Illness
false positive CH NBS
Blood sample is drawn too early, prior to 24hrs of life
1 cause of hypothyroidism worldwide
iodide deficiency
most common thyroid dyshormonogenesis cause
organification defect
Hemangiomas effect on thyroid?
consumptive hypoT
type 3 deiodinase
can be severe hypo
hemangioma could be not visible - ex liver
Pendred syndrome
PDS gene
SLC26A4 gene
defect in transport of I to colloid
presentation: goitre, later childhood
10% have SNHL
causes of poor neurodevelopmental outcomes that are associated with CH
- Late diagnosis
- Late initiation of treatment
- Undertreatment
- Overtreatment
- Prolonged time taken to normalize of thyroid function (TSH)
- Poor attendance of clinic visits
Poor control during first year of life
Associated markers for poor neurodevelopmental outcomes, CH severity:
○ Initial T4
○ Initial TSH
○ Bone immaturity
§ Ie: absent knee epiphyses at term
○ Etiology (ie: thyroid agenesis)
○ Parental education
○ Rural setting
○ Access to NBS program
goal for tx of CH
TSH - upper half of the reference range during the first 3 years of treatment
characteristic of hasimoto
- Characterized by lymphocytic infiltration of the thyroid gland, which results in thyromegaly
neonatal signs of hypothyroidism
○ macroglossia
○ umbilical hernia
○ large anterior fontanelle with wide sutures
○ jaundice
○ cool to touch
○ hypotonia
○ delayed reflexes
Drugs that interfere w thyroid function - need to increase Synthroid
Inhibition of levothyroxine absorption (will need more!)
○ Iron
○ Calcium
○ Soy
○ PPI
○ Aluminum hydroxide
○ Colestyramine
○ Colestipol
○ Sucralfate
○ Raloxifene
Increased hepatic metabolism (will need more!)
○ Phenobarbitol
○ Phenytoin
○ Carbamazepine
○ Rifampin
○ TKI (Imatinib, axitinib, motesanib, vandetanib)
Rexinoids
Increased thyroxine binding globulin levels (will need more - more T4 bound to TBG so less is free)
○ Estrogen
○ Raloxifene
○ Tamoxifen
○ Methadone
○ Mitotane
Fluorouracil
Drugs that interfere w thyroid function - need to decrease Synthroid
Decrease hepatic metabolism (will need less!)
○ Metformin (not great evidence)
Inhibition of 5’ deiodinase
○ Propylthiouracil
○ Methimazole
○ Propranolol
○ Glucocorticoids
○ Iodide
Decreased thyroxine binding globulin levels (will need less!)
* Androgens
* Glucocorticoids
* Nicotinic acid
effect of amiodarone on TFT
- inhibiting TH entry into peripheral tissues
- inhibiting type I 5’-deiodinase activity which converts T4 to T3 and reverses T3 to T2. (This inhibition may continue months after amiodarone withdrawal.)
- inhibiting type II 5’-deiodinase which converts T4 to T3 in the pituitary
- failure to escape from the Wolff-Chaikoff effect
- precipitating or exacerbating preexisting organ-specific autoimmunity in susceptible individuals, such as those with autoimmune thyroiditis
dysregulating thyroid hormone synthesis, especially in patients with thyroid nodules or goiter.
effector lithium on thyroid function
- inhibits TH synthesis and secretion
- usually hypothyroid
- increased AITD
v rarely hyperthyroid
Cystinosis
- what is it
-features
Lysosomal storage dz
Photophobia
Renal problems
Hypothyroidism
Labs in hypoT
- Hypercholesterolemia (↑ LDL)
- Hyponatremia (increased total body water)
- Anemia (↓ erythropoietin, ↓ oxygen requirement)
- Elevated creatinine kinase and LDH (from skeletal muscle)
- Reduced GFR
- Elevated liver transaminases
Exam hypoT
- Reduced heart rate and decreased cardiac contractility
- Delayed relaxation phase of DTRs
- Dry skin (↓ sweat and sebaceous gland activity)
- Periorbital puffiness, non-pitting edema (hyaluronic acid)
Myxedema - exam
-Altered mentation
-Alopecia
-Bladder dystonia and distension
-Cardiovascular
–Elevated diastolic blood pressure—early
–Hypotension—late
–Bradycardia
-Delayed reflex relaxation
-Dry, cool, doughy skin
-Gastrointestinal
–Decreased motility
–Abdominal distension
–Paralytic ileus
–Fecal impaction
–Myxedema megacolon—late
-Hypoventilation
-Hypothermia
-Myxedematous face
–Generalized swelling
–Macroglossia
–Ptosis
–Periorbital edema
–Coarse, sparse hair
-Non-pitting edema
Myxedema labs
-Anemia
-Leukopenia
-Elevated CK
-Elevated creatinine
-Elevated transaminases
-Respiratory
-Hypercapnia
-Hypoxia
-Respiratory acidosis
-Hyperlipidemia
-Lytes & glucose:
–Hypoglycemia
–Hyponatremia
tx myxoedema coma
- ICU
- ABCDE
- Levothyroxine
- Steroids (until AI can be rules out)
=/- Abx if concern infection