Thyroid Disorders Flashcards
Hypothalamic-Pituitary Thyroid Axis
- Hypothalamus secretes thyroid-releasing hormone (TRH)
- Pituitary secretes thyroid-stimulating hormone (TSH)
- TSH stimulates formation of tetraiodothyronine (T4) or “Thyroxine” & some of the formation of triiodothyronine (T3)
2 types of thyroid secretory cells
Follicular - produces thyroid hormones
- Thyroxine (T4)
- Triiodothyronine (T3)
Parafollicular (“C cells”) - secretes calcitonin
Under the influence of thyroid stimulating hormone (TSH) _____ is taken into the follicular cell
iodide
In the presence of _____, iodide is oxidized (combined with O2) to iodine
thyroid peroxidase
Iodine then binds to the ____ portion of the _____ within the colloid of the follicular cell
tyrosine; thyroglobulin molecule
Colloid of the follicle stores ____ (~3 months worth)
thyroglobulin
T/F thyroglobulin is released with T3 and T4
F
> 99% of T3 & T4 entering the blood bind with plasma proteins, mostly to _____
thyroxine binding globulin
The unbound 1% of T3/T4 circulating in the blood is
Physiologically inactive
Is T3 or T4 more physiologically active?
T3
What happens to T4 while circulating
T4 is changed in to T3 at the intracellular level by several types of 5’ deiodinase
1/2 life of T3
24 hours
1/2 life of T4
5-7 days
Thyroid cell prodicing calcitonin
Para-follicular cell
Solubility of calcitonin
Water Soluble
Peptide hormone travel in the blood & binds on receptor proteins
1/2 life of Calcitonin
50-80 min
Four main metabolic functions of T3/T4
↑ Basal Metabolic Rate
↑ Cardiac Output
Stimulates BONE maturation & growth
↑ Metabolism
BRAIN Benefits of T3/T4
clear thinking, improved mood, & energy
Most common cause of hyperthyroidism
Graves Disease
Hyperthyroidism primary causes
- Graves Disease (autoimmune)
- Subacute thyroiditis ( “DeQuervain” thyroiditis
Cause = viral infection) - ↑ iodine intake
- ↑intake of exogenous thyroid hormone
- Drugs (Amiodarone)
Hyperthyroidism secondary causes
- ↑ TSH: Anterior pituitary adenoma
- ↑ TRH secretion: Hypothalamic tumor
Grave’s Disease (Diffuse Toxic Goiter) is an Autoimmune disorder of the thyroid gland, characterized by ____
↑ synthesis & release of thyroid hormones.
Grave’s Disease epidemiology
More common in women than men 8:1
Associated with ↑ antibodies, exophthalmos, pretibial myxedema, onycholysis (separation of nail from its bed)
↑ risk other autoimmune disorders
refers to what
Graves disease
Subjective complaints (SYMPTOMS) of Graves disease
Sweating, weight loss or gain, anxiety, palpitations, loose stools, heat intolerance, irritability, fatigue, weakness, menstrual irregularity
Hyperthyroidism Clinical Presentation of HEENT
- Diffuse non-tender goiter
- Exophthalmos
- Proptosis
Clinical Presentation of Hyperthyroidism, CV
Arrhythmias ex: atrial fibrillation
↑HR
↑BP
Clinical Presentation of Hyperthyroidism, Neuro
Muscle weakness
Sudden paralysis
Resting tremor
Hyperreflexia
Clinical Presentation of Hyperthyroidism, Extremities
LE edema
Pretibial myxedema
Fingernail clubbing
Clinical Presentation of Hyperthyroidism, Skin
Warm, moist skin
Facial flushing
Pretibial myxedema
What is Pretibial Myxedema (Thyroid Dermopathy) in Hyperthyroidism?
Discoloration
shiney pink to purple/brown
Induration- non pitting
“Orange peel”
Deposition of hyaluronic acid
Hyperthyroidism Diagnostic labs
↓ TSH (Primary), ↑ TSH (Secondary)
↑ FT4 and T3
Thyrotropin receptor antibodies (TRAb)
Anti-Thyroid peroxidase antibody (Anti-TPOAb) - 75% (MOST COMMON test for autoimmune thyroid disease)
Initially presents as hyperthyroidism but eventually results in hypothyroidism
Can be acute, subacute, or chronic
Describes what
Thyroiditis
Subacute Granulomatous thyroiditis in hyperthyroidism
“de Quervain’s thyroiditis”
Typically caused by viral infections
- Painful, tender thyroid on physical exam
- Possible prodrome of myalgias, pharyngitis, low-grade fever
Diagnosis for Subacute Granulomatous thyroiditis
Physical exam
↑ ESR/CRP
Low or absent anti-TPO antibodies
Mild leukocytosis
Treatment for Subacute Granulomatous thyroiditis
NSAIDs for thyroid pain & tenderness
Oral steroids (prednisone) for more severe symptoms
Self-limiting and usually improves or resolve
~ 4-6 weeks
describes what
Subacute Granulomatous thyroiditis
Postpartum Subacute Thyroiditis etiology in Hyperthyroidism
- Human chorionic gonadotropin binds to TSH receptors, Causes hyperthyroidism & ↑ serum thyroxine-binding globulin
- Onset within 12 months after delivery
- Hyperthyroidism initially → hypothyroidism → euthyroid
Postpartum Subacute Thyroiditis PE
painless firm goiter
NO exophthalmos
NO myxedema
Postpartum Subacute Thyroiditis diagnosis
↑ anti-TPO titer
autoimmune
Normal ESR/CRP
Postpartum Subacute Thyroiditis treatment
- Symptomatic relief with beta blockers (propranolol beta blocker of choice during breastfeeding)
- Levothyroxine if symptomatic hypothyroidism, tapered & stopped after 6-9 months
Subclinical Thyroiditis in Hyperthyroidism
- ↓TSH & normal FT4/T3
- Cause: Over-dosing with thyroid hormone
- Progression to overt hyperthyroidism
- Typically reverts to normal within 2 years.
↑ risk of atrial fibrillation
Subclinical Thyroiditis treatment
- > 65 yo and those with heart disease or osteoporosis with TSH <0.1
- Pts with persistently low TSH (<0.1) & asymptomatic
- Observe pts with TSH 0.1 –0.4 & repeat testing
Temporary symptomatic relief of hyperthyroidism
- β-Adrenergic blockade: Anti–Tachycardia, Tremor, Anxiety & Diaphoresis
- Artificial tears: exophthalmos
- Topical glucocorticoids: pretibial myxedema, Anti-inflammatory
Definitive Treatments for Hyperthyroidism
- Antithyroid drugs: Methimazole & Propylthiouracil (PTU)
- Thyroidectomy
- Radioactive iodine ablation (RAIA): Good for women planning pregnancy in future
Contraindications (relative) for B-blockers in hyperthyroidism management
Asthma or COPD
Raynaud’s
Pregnancy (except labetalol)
Methimazole (Tapazole®) MOA
1st line
Inhibits synthesis of thyroid hormone by blocking oxidation of iodine in thyroid gland
blocks synthesis of thyroxine (T4) and triiodothyronine (T3)
Propylthiouracil (PTU) MOA
1st line if 1st trimester or breastfeeding
Inhibits synthesis of thyroid hormone by blocking oxidation of iodine in thyroid gland
blocks synthesis of T4 and T3
Indications of Antithyroid drugs/Thionamides
Hyperthyroidism
Thyroid storm (adjunct),
Pre-treatment
- Thyroid surgery
- Radioactive iodine treatment
Side effects of Antithyroid drugs/Thionamides
Rash
itching
agranulocytosis
pancytopenia
hepatotoxicity
teratogenicity
_____ can be safe in breastfeeding
propanalol
Thyroid ablation involves using what ___
Radioactive Iodine
What does thyroid ablation
- Destroys thyroid tissue
- No ↑ of subsequent thyroid cancer, leukemia, or other malignancies
Contraindications for Radioactive Iodine
Pregnancy & lactation
Mothers without childcare
Indications for Thyroid ablation
Graves
toxic adenoma
multinodular goiter
Side effects of thyroid ablation
Infertility
N/V
dry mouth
Follow-up for Thyroid ablation
The resulting hypothyroid state after RAIA requires lifelong thyroid hormone replacement
Monitor for hypoparathyroidism
Thyroidectomy indications
Graves (total thyroidectomy)
toxic multinodular goiter
thyroid malignancy
large goiters
Contraindications for Thyroidectomy
comorbidities that influence surgical risk
Side Effects of Thyroidectomy
Recurrent laryngeal nerve palsy, hoarseness
hypoparathyroidism
_____ Usually requires patient be euthyroid prior to surgery
Thyroidectomy
Thyroid Strom “thyrotoxic crisis”
Sudden release of large amounts of thyroid hormone
precipitating factors to Thyroid Strom “thyrotoxic crisis”
Abrupt stop of anti-thyroid meds
Thyroid surgery
Non-thyroid surgery trauma
Acute infections
Iodinated contrast medium
Burns
Medication SE
Symptoms of a Thyroid Storm
fever (as high as 104-106°F)
Tachycardia
heart failure
Arrhythmia
Diaphoresis
N/V/D
Irritability, delirium
Seizures, coma
Death (cardiac arrest)
PE findings for a thyroid storm
Fever
Tachycardia
Goiter
Hand tremors
Moist & warm skin
Hyperreflexia
Thyroid Strom “thyrotoxic crisis” Diagnosis
High FT4/T3 & low TSH
Others:
Hypercalcemia
Hyperglycemia
abnormal LFTs
↑ or ↓WBC
Imaging: CXR, head CT
EKG: Monitor for arrythmias
Thyroid Strom “thyrotoxic crisis” Treatment
IV fluid repletion
Supplemental O2
Cooling blankets
Acetaminophen (Tylenol)
Treat precipitating factors
IV Beta-blocker
Loading dose of PTU
Supersaturated potassium iodide (SSKI)
IV steroids
Epidemiology of Hypothyroidism
> 1% of population
5% over 60 yo
PRIMARY CAUSES of Hypothyroidism
- Failure of the thyroid gland (Hashimotos most common, 95%)
- Iodine deficiency
- Drugs (Amiodarone, interferon)
- Iatrogenic
SECONDARY CAUSES of Hypothryoidism
TSH deficiency
TRH deficiency: Mass lesions, congenital/genetic abnormalities/acquired (concussions), functions (aging/anorexia)
HASHIMOTOS THYROIDITIS
Autoimmune disease
Patients can frequently have other side effects due to co-occurring autoimmune diseases (Addison disease, hypoparathyroidism, diabetes mellitus)
Clinical Presentation of Hypothyroidism
Weakness, fatigue, lethargy
Arthralgia’s, carpal tunnel syn.
Cold intolerance, Raynaud’s syndrome
Constipation
weight gain
Depression
Menorrhagia
Headache
Objective findings (SIGNS) of Hypothyroidism
Bradycardia
Thinning, brittle nails, & hair
Peripheral edema, puffy face & eyelids
Skin pallor or yellowing
Delayed deep tendon reflexes
Palpably enlarged thyroid (GOITER)
hoarseness
Two forms of Hypothyroidism
- Goiter
Hashimoto’s
Iodine deficiency
Genetic
Drugs - Atrophic
Radiation Therapy
Thyroid agenesis or genetic mutations
Thyroidectomy
Diagnostics for Hypothyroidism
TSH - if ↑, thyroid gland is being asked to make more T4
if FT4↓ = primary hypothyroidism
if FT4 normal = subclinical hypothyroidism
If TSH ↓ & FT4 ↓ = secondary hypothyroidism
Management of hypothyroidism
- L-thyroxine (Levothyroxine, Levoxyl®, Synthroid®): Synthetic T4
Contraindications of L-thyroxine (synthyroid)
Drugs that affect GI absorption (adjust dosing time)
Bile acid resins/ sequestrants - cholestyramine, colesevelam
PPIs - omeprazole, pantoprazole
Overt thyrotoxicosis, acute MI, adrenal insufficiency
Not for weight loss or obesity in euthyroid pt
Side Effects of L-thyroxine (Levothyroxine, Levoxyl®, Synthroid®)
heat intolerance
Tachycardia
arrhythmias/atrial fibrillation elderly
Tremors
weight loss
Follow-up for L-thyroxine (Levothyroxine, Levoxyl®, Synthroid®)
Target TSH after 4-6 weeks
q6-12 months if at stable dose
Desiccated thyroid extract (Armour Thyroid) usage for Hypothyroidism
Mostly commonly thyroid hormone from pig thyroid
Ratio of T4:T3 = 4:1
physiologic ratio is 13:1 - 16:1
No strong evidence for desiccated thyroid over monotherapy with levothyroxine
Liothyronine (Cytomel®)
Synthetic T3
↑ basal metabolic rate
↑ utilization & mobilization of glycogen stores
Promotes gluconeogenesis
Side Effects of Liothyronine (Cytomel®)
Tachycardia
Hypotension
Slight risk for acute MI
is Liothyronine (Cytomel®) safe in pregnancy?
Yes, caution in breastfeeding
Factors affecting thyroid hormone absorption
Age
Malabsorption syndromes
Meds
Weight gain
Pregnancy
Life threatening form of hypothyroidism
Myxedema Crisis
Mortality rate almost 100% without treatment
Mortality rate 20-50% with optimal treatment
describes what
Myxedema Crisis
Epidemiology of Myxedema Crisis
Most common → elderly women who have had a stroke or stopped taking thyroxine medication
Underlying infection, cold exposure, hypoglycemia, hypotension, hypoventilation
Severe Adult Hypothyroidism clinical presentation
Swelling of the skin & underlying tissues
Waxy consistency: firm & inelastic
Non-pitting edema
Dry skin & hair: frowzy hair
Dull apathetic appearance, swollen lips, thickened nose
Severe Adult Hypothyroidis Cause
Infections: UTI, pneumonia, influenza
Meds: Amiodarone , narcotics, lithium, not starting thyroid replacement during hospitalization
Trauma, surgery
Severe Adult Hypothyroidism: Diagnostics
Hypoglycemia
↓ Na+
↓ O2
↓ ventilation
↑ CO2
↑CPK
Severe Adult Hypothyroidism management in ICU
- stabilize pts who are hemodynamically unstable
- focus on repleting fluid & electrolytes
- IV thyroid replacement (T4 alone) → - oral replacement preferred, if possible
- Empiric ABX (if indicated)
- IV hydrocortisone
EUTHYROID SICK SYNDROME occurs in ___
Pt without known thyroid disease, with ↓ serum FT4 & normal TSH
Do not use levothyroxine for ____
EUTHYROID SICK SYNDROME
Most sensitive test for primary hypo/hyper-thyroidism
Thyroid-stimulating hormone (TSH)
SINGLE best screening test for HYPOthyroidism
Thyroid-stimulating hormone (TSH)
More sensitive test for hyperthyroidism
Free Triiodothyronine (FT3)
Free Thyroxine (FT4) is ___
commonly tested along with TSH
Presence of _____ is diagnostic for Graves disease
Thyroid stimulating immunoglobulin (TSI)
Good cancer marker post-thyroidectomy
Thyroglobulin
Good for Diagnosis & monitoring ofmedullary thyroid carcinoma
Calcitonin
Anti-thyroid antibody present in Grave’s & Hashimotos Thyroiditis
Anti-thyroid peroxidase (TPO) ab
Low TSH, Low FT4/FT3
Central hypothryroidism
High TSH, Low FT4/FT3
Primary hypothyroidism
Low TSH, High FT4/FT3
Primary hyperthyroidism
High TSH, High FT4/FT3
Secondary hyperthyroidism
Imaging test of choice for Thyroid disorder testing
Ultrasound
_____ is imaging that can help to Confirm cancerous nodule or Graves dz
Radioiodine scan
Best diagnostic method for thyroid cancer
Fine-needle Aspiration (FNA) Biopsy
Enlargement of the entire thyroid gland
Goiter
Single or Multinodular
small round lump(s) from the surrounding tissue on thyroid
Nodule
Types of Goiters
- Hypothyroid (Hashimoto): Fibrosis, Iodine deficiency overstimulation
- Hyperthyroid (Graves): Overproduction
- Subacute: viral infection
Types of thyroid nodules
- Non-toxic: No abnormal production of thyroid hormones
- Toxic: Abnormal production of thyroid hormones
Epidemiology of thyroid noduels
Common: Palpable nodules in 5% of women & 1% of males.
With the use of CT, MRI, & ultrasound detection rates of incidental nodules has risen to 30-60%.
Any nodule ≥___ cm should have Further testing for function & malignancy
1
Nodules that uptake ____ are rarely malignant
RAI
____; BEST method to assess a thyroid nodule for malignancy
FNA: fine needle aspiration?
4 types of Painless swelling in the region of the thyroid (thyroid cancer)
Papillary thyroid carcinoma
Follicular (differentiated) thyroid carcinoma
Medullary thyroid carcinoma
Anaplastic thyroid carcinoma
Most common thyroid malignancy
Papillary Thyroid Carcinoma
T/F Follicular Thyroid Carcinoma is generally more aggressive than papillary
T
Serum calcitonin is elevated in this thyroid cancer
Medullary Thyroid Carcinoma
Carcinoembryonic antigen (CEA)
blood test for cancer
Typically presents in older patients as a rapidly enlarging mass in a multinodular goiter.
Anaplastic Thyroid Carcinoma
Treatment of thyroid cancers
Surgical Removal is the treatment of choice for thyroid carcinomas
Post thyroidectomy: patient will need levothyroxine for life
Low TSH, Normal FT4/FT3
Subclinical Hyperthyroidism
High TSH, Normal FT4/FT3
Subclinical hypothyroidism
Normal TSH, High FT4/FT3
Acute psychiatric illness
Drug effect
(amiodarone)
Normal TSH, Low FT4/FT3
Euthyroid sick syndrome
Drug effect
(amiodarone, interferon…)
Can also be caused by Low TSH, High FT4/FT3
