Thyroid Flashcards
1. Define the following terms: Goiter, Euthyroid, Thyrotoxicosis, Thyroiditis 2. Define the following diseases/disorders to include the pathophysiology, epidemiology, risk factors (if any), clinical presentation, physical findings, diagnostic evaluation, differential diagnoses, and management plan: Hypothyroidism, including euthyroid sick syndrome and myxedema crisis; Thyroiditis, including Hashimoto's thyroiditis, postpartum thyroiditis, subacute (DeQuervain) thyroiditis, and suppurative thyr
This organ rising when swallowing. Roughly 4 cm long; each lobe 2cm wide.
Thyroid
Active form of thyroid hormone
T3
Storage form of thyroid hormone; and lives longer than the active form
T4
Majority of T3 and T4 in the body is bound to what two proteins?
Thyroid Binding Globulin and Albumin
Ratio of T3 to T4 in the body (T3:T4)
1:40
T3 or T4 is more potent?
T3
Half life of T3
1 day
Half life of T4
1 week
What exogenous item is necessary for ideal thyroid function?
Iodine
Where do we get iodine?
Diet and fortified salt
How much iodine do we intake on average?
500 mcg
What’s the least amount of iodine we should intake per day?
150 mcg
Excess iodine can lead to?
- Autoimmune thyroid disease
- Hypothyroidism as a result of autoimmune disease
- Thyroid nodule development!
What hormone(s) from the hypothalamus controls release of thyroid hormone?
TRH (Thyroid Releasing Hormone)
What hormone(s) from the pituitary gland (adenohypophysis) controls release of thyroid hormone?
TSH (Thyroid Stimulating Hormone)
What hormone(s) from the Thyroid controls release of thyroid hormone?
Thyroxine (T4)
Tri-iodo-thyro-ine (T3)
Describe the positive feedback of Thyroid Hormone Secretion.
Tea Time PTL:
TRH from hypothalamus to the PG stimulating release of TSH which goes to the thyroid stimulating the release of TH
Describe the negative feedback of Thyroid Hormone Secretion
TH in excess can cause inhibitory affects at the hypothalamus or PG to reduce TRH or TSH secretion, respectively.
What happens when you have iodine deficiency?
Goiter
How does iodine deficiency lead to Goiter?
Low iodine –> T3/T4 not synthesized
When TH is LOW, TRH secretion is increased by the Hypothalamus, which leads to an increase in TSH by the PG which stimulates Thyroid to create TH. TH accumulates because the precursors to create T3 and T4 are not there, causing an enlargement of the thyroid gland.
Primary causes of Hypothyroidism
- Autoimmune (most common)
- Iatrogenic (medically induced)
- Drug induced
- Congenital
Secondary causes of Hypothyroidism
Loss of signaling from PG (aka Central Hypothyroidism)
Physical Exam Findings of Hypothyroidism
Dry, brittle hair with hair loss
Edema of face and eye lids
Thick, heavy tongue with slow speech and coarse voice
Decreased perspiration
Bradycardia (slow HR)
Weight gain (decreased metabolism)
Skin is pale, dry, cold and has rough texture
Lethargic, poor memory, slower, expressionless
Menorrhagia (Changes in menstruation; commonly prolonged and heavy)
Cold intolerance
Delayed deep tendon reflexes
Why do we see these physical exam findings in hypothyroidism?
Because TH stimulates everything in the body, so where there isn’t enough everything SLOWS!
What is the effect of T3/T4 on the body?
Increases mitochondria, ATPase activity, and modulates cholesterol metabolism. This leads to increased energy turn over, a rise in O2 consumption, and development of heat. T3 also stimulates action of Epi and Glucagon and GH.
What is the effect of T3/T4 on the body?
Increases mitochondria, ATPase activity, and modulates cholesterol metabolism. This leads to increased energy turn over, a rise in O2 consumption, and development of heat. T3 also stimulates action of Epi and Glucagon and GH.
Physical Exam Findings for Myxedema
Slow speech Absence of sweating Constipation Peirpheral Edema (Hard pitting edema is unusual but can happen) Pallor Hoarseness Decreases sense of taste and smell Muscle cramps, aches, and pains Dyspnea Weight changes (usually gain, but weight loss isn't rare) Diminished auditory acuity Pleural/Pericardial effusions (rare)
Physical Exam Findings for Myxedema
Slow speech Absence of sweating Constipation Peirpheral Edema (Hard pitting edema is unusual but can happen) Pallor Hoarseness Decreases sense of taste and smell Muscle cramps, aches, and pains Dyspnea Weight changes (usually gain, but weight loss isn't rare) Diminished auditory acuity Pleural effusions (rare)
Lab findings for Hypothyroidism
T4 levels LOW
In primary, TSH levels will be HIGH
In secondary, TSH levels will be LOW
Anemia
Why is TSH decreased in secondary (central) hypothyroidism?
Because there is an issue at the PG causing an inability to secrete TSH
Why is TSH decreased in secondary (central) hypothyroidism?
Because there is an issue at the PG causing an inability to secrete TSH
Why is TSH low in Hyperthyroidism?
Elevated T3 and T4 will inhibit TSH secretion
How to treat hypothyroidism?
Levothyroxine (aka Synthroid)
Avg dose: 125 mcg in the morning before food
Be sure to not take any iron, calcium, or Maalox.
If heart disease is present, start with a lower dosage.
Dosage dependent on weight (1.6 micrograms per kilogram)
How to treat hypothyroidism?
Levothyroxine (aka Synthroid)
Avg dose: 125 mcg in the morning before food
Be sure to not take any iron, calcium, or Maalox.
If heart disease is present, start with a lower dosage.
Dosage dependent on weight (1.6 micrograms per kilogram)
If elevated thyroglobulin antibody (TgAb) or elevated Antithyroid peroxidase antibody (TPOAb) along with swelling of thyroid indicates:
Hashimoto’s Thyroiditis
If elevated antithyroglobulin antibody (TgAb) or elevated Antithyroid peroxidase antibody (TPOAb) along with swelling of thyroid.
Hashimoto’s Thyroiditis
Thyroid gland is diffusely enlarged, firm, finely nodular, and pt may complain of neck tightness
Hasimoto’s Thyroiditis
Enlarged thyroid that is very tender and painful. Sometimes febrile state of patient if they had a viral infection before. Can complain of dysphagia as well.
Subacute (DeQuervain) Thyroiditis
Enlarged thyroid that is very tender and painful. Sometimes febrile state of patient if they had a viral infection before.
Subacute Thyroiditis
How do you treat subacute thyroiditis?
ASA or NSAIDs
If untreated, what can happen?
More inflammation, eventual fibrosis and scarring. This can lead to decreased function of the gland.
If untreated, what can happen?
More inflammation, eventual fibrosis and scarring. This can lead to decreased function of the gland.
Subacute Thyroiditis would present on labs (over time) as …
Thyrotoxicosis (symptom of hyperthyroidism) for a few weeks, then hypothyroidism for about 4-6 months) then normal thyroid levels (about 12 months later)
How do you treat subacute thyroiditis?
ASA to help with pain and inflammation
How do you treat subacute thyroiditis?
ASA to help with pain and inflammation
Febrile patient comes in with severe pain, tenderness, redness, and fluctuation in the thyroid region. Pt has a history of thyroid disease.
Suppurative Thyroiditis
Cause of Suppurative Thyroiditis?
Bacterial infection of the thyroid. This is an emergency and VERY painful. This is very rare due to the encapsulation, high iodine content, and good blood/lymph supply. Chance increases with pre-existing thyroid disease.
Treatment of Myxedema coma
Steroids (hydrocortisone 100 mg Q8 for at least 48 hours, then decrease to 50 QD to off in 1 week.
Replace IV thyroid replacement, change to oral after 72 hours
IV fluids/warming blankets
ICU monitoring (EKG and lytes and BP/Temp)
When serum levels of T4 and T3 are excessive for an individual.
Thyrotoxicosis (Hyperthyroidism)
Treatment of Myxedema coma
Steroids (hydrocortisone) 100 mg Q8 for at least 48 hours, then decrease to 50 QD to off in 1 week
Physical Findings of Hyperthyroidism?
Exophthalmos (lid lag and stare) Fine, silky hair with hairloss Sweating Weight loss (sometimes gain) Increased Appetite Loose stools Anxiety Heat Intolerance Irritability Fatigue Weakness Menstrual Irregularity (or Amenorrhea) Tachycardia (so much that they do not get restorative rest) Angina pectoris Warm, moist skin Tremors Brisk deep tendon reflexes
Goiter with bruit; ophthalmopathy with very vascular gland.
Grave’s disease
Goiter with bruit; ophthalmopathy with very vascular gland.
Grave’s disease
Causes of Hyperthyroidism?
Grave's Disease (autoimmune condition) Toxic Adenoma and Multinodular Goiter (nodules become autonomous) Thyroid Storm (causes by any cause of hyperthyroidism, but the severe spectrum)
Thryrotoxicosis; most common in women (8:1); goiters are more prevalent in fresh water and lake countries due to lack of iodine in fresh water.
Grave’s Disease
Physical Exam Findings of Grave’s Disease
Thyrotoxicosis; Goiter; Dermopathy; Eye Disease
Physical Exam Findings of Grave’s Disease
Thyrotoxicosis; Goiter; Dermopathy; Eye Disease
Sympathetic overactivity mediated by increased alpha-adrenergic receptors in some tissues is thought to cause _______ in Grave’s Disease. Also due to fat tissue build up and muscle inflammation behind the eye.
Exophthalmos
How to check for lid lag?
Have the patient follow the examiner’s finger as it is moved up and down. The patient has lid lag if sclera can be seen above the iris as the patient looks downward. Lid stay up during this test.
Non-piting scaly thickening and induration of the skin, most commonly over the lower legs, especially the pretibial areas. Usually has one or more well-demarcated papules or nodules several cm in diameter.
Pretibial Myxedema
This condition occurs in about 5% of patients who have Grave’s disease. Typically presenting, after already having hyperthyroidism and ophthalmopathy.
Pretibial Myxedema
Due to tachycardic effects associated with hyperthyroidism, this may present in the patient. Note: This could potentially lead to heart failure.
Atrial Fibrillation
Workup for Hyperthyroidism
- Check labs – if low TSH and high T4/T3, REPEAT labs!
- If repeat labs show the same thing, obtain a thyroid uptake or an ultrasound.
- Check TSI antibodies
- Start treatment!
Treatment for Hyperthyroidism
- PTU (propylthiouracil) – decreases hormone synthesis.
- Methimazole and PTU both decrease release of TH and peripheral conversion of T4 –> T3
Note: YOU MUST check CBC and LFTs before starting.
When should PTU be used?
Hyperthyroid patient in a thyroid storm or in the 1st trimester of pregnancy.1
Reason why PTU is not preferred in Hyperthyroidism treatment.
3rd leading cause of drug-related hepatitis
Autoantibodies that can bind to TSH receptors in thyroid cell membranes can cause?
Hyperthyroidism
The key antibody that binds to TSH receptors in thyroid cell membranes can cause Grave’s Disease is __________.
TSH-receptor stimulating antibody (TSH-R Ab[stim])
On a histology study of a patient with Grave’s disease, you will see a _______ colored staining, which isn’t present in normal thyroid tissue. This color staining is due to the presence of ________.
Brown; HLA class II
Second most common cause of hyperthyroidism. Much more common in the elderly. Commonly forms benign nodules (95%).
Toxic Adenoma and Multinodular Goiter
If nodules are present on the thyroid, what should you do next?
Should be evaluated for cancer!
Radioactive Iodine Scan will show a concentrated on a thyroid scan in what disease?
Toxic Adenoma
Condition that presents with one or more focal areas of increased radioiodine uptake
Toxic Multinodular Goiter
Two types of nodules in Goiter
Solid vs. Cystic
Complication of poorly treated thyrotoxicosis and additional stress. Very severe form of Hyperthyroidism. Very rare, but when present mortality is high.
Thyroid Storm
Patient presents with marked delirium, severe tachycardia, vomitting, diarrhea, dehydration, and a very high fever.
Thyroid Storm
How do you treat Thyroid Storm?
- Admit to ICU
- IV fluids/cooling measures
- Monitor electrolytes, BP, and temperature
- Hydrocortisone (steroids help decrease T4/T3 conversion and release from thyroid)
- Start PTU or MMI
- Start beta blocker
Patient presents with a painless swelling in the region of the thyroid. Thyroid function testing was completed and everything came back normal. A thyroid needle aspiration was completed and came back positive. Note: Patient did have a history of irradiation of the head/neck.
Thyroid Cancer
The preferred biopsy to obtain thyroid tissue for analysis in detecting or ruling out the presence of cancer.
Fine Needle Aspiration (Positive = cancerous)
If suspected cancer, what must you do?
Refer to Endocrinology!
Prevalence of Thyroid Carcinoma is more in which sex?
Females (3:1)
Most common types of thyroid cancer?
Papillary and Follicular
Least common types of thyroid cancer?
Anaplastic and Medullary
Highest mortality rate of thyroid carcinoma occurs in which type of carcinoma?
Anaplastic (98%)
Lowest mortality rate of thyroid carcinome occurs in which type of carcinoma?
Papillary (6%)
Note: Follicular 24% and Medullary 33%
Prognosis of Thyroid Carcinoma
Papillary > Follicular > Medullary > Anaplastic
Other factors for carcinomas/cancers in determining prognosis
Size # of Tumors Encapsulated Vascular invasion Lymph Nodes Distant Metastases Age Sex Time
Risk Factors for Thyroid Cancer
- History of thyroid cancer in one or more first degree relatives
- History of external beam radiation as a child
- Exposure to ionizing radiation in childhood or adolescence
- Prior hemithyroidectomy with discovery of cancer.
- FDG avidity on PET scanning
- MEN2/FMTC-assc RET proto-oncogene mutation
- Calcitonin > 100 pg/mL
- MEN, Multiple Endocrine Neoplasia
- FMTC, Familial Medullary Thyroid Cancer
Treatment for Thyroid Cancer
- Ultrasound guided Fine Needle Aspiration
- Total Thyroidectomy
- Iodine 131 Ablation
- Serum Thyroglobulin for follow up
State of having a normal functioning thyroid gland
Euthyroid
Autoimmune thyroiditis that occurs soon after delivery.
Postpartum Thyroiditis
Condition where there is an accumulation of fetal cells in the maternal thyroid during pregnancy.
Microchimerism in postpartum thyroidism
If a woman has postpartum thyroiditis, they have a ____ chance of getting it again in a subsequent pregnancy.
70%
Risk Factors for Postpartum thyroiditis
- High levels of Thyroid Peroxidase Antibody in first trimester
- History of postpartum thyroiditis
- Other autoimmunity disease
- Family history of Hashimoto thyroiditis
No apparent thyroid disease, but still seeing abnormal thyroid function test results, such as low serum T3 and low serum T4.
Euthyroid Sick Syndrome
Order of Operations for Thyroid Cancer
- Palpable unilateral nodule
- Ultrasound to check structural. If “hot” probably benign
- Check Thyroid Functioning (with TSH, etc. testing)
- Fine Needle Biopsy if suspected of being cancerous due to abnormal functioning and anatomy.
**Note: this is from the Case Study lecture, which varies a bit from the original lecture, where US and FNA are both done to check for cancer after finding abnormal PhysEx or TSH testing.
Potential causes/Increased Likelihood of Euthyroid Sick Syndrome
- Pt with severe illness
- Caloric Deprivation
- Major Surgery
Why would a major surgery cause Euthyroid Sick Syndrome (normal thyroid and abnormal T3 or T4)?
Major surgeries can cause an accelerated peripheral metabolism of serum T4 in order to reverse T3 activity.
Why would a critical illness cause Euthyroid Sick Syndrome (normal thyroid and abnormal T3 or T4)?
In critically ill patients, there is an inhibitor of thyroid hormone binding to the TBP. Causing T3 and T4 to be low.
** Fun Fact: Low T4 in a non-thyroid illness tends to be a bad prognosis :( #NotSoFun
Serum _____ tends to be suppressed in severe nonthyroidal illness, making the diagnosis of concurrent hypothyroidism difficult. What could help you think it is concurrent hypothyroidism?
TSH levels; If goiter is apparent, it could be concurrent hypothyroidism.
This refers to severe, life-threatening manifestations of hypothyroidism that can cause impaired cognition (confusion to somnolence to coma).
Myxedema Crisis
This life-threatening manifestation of hypothyroidism is most common in elderly women with a history of stroke or have stopped their thyroxine medication.
Myxedema Crisis
What can cause a myxedema crisis?
Underlying Infection
Cardiac, Respiratory or CNS Illness
Cold Exposure
Drug use
Symptoms of a Myxedema Crisis
Cognitive Impairment Severe hypothermia Hypoventilation Hyponatremia Hypoglycemia Hypotension
Sign of thyrotoxicosis where the nail is separated from the bed.
Onycholysis
Onycholysis is most common in which disease?
Grave’s Disease
Cure for Onycholysis?
Spontaneously gets better as Grave’s disease is treated.
Clubbing and swelling of the fingers and toes
Acropachy
Is acropachy a common manifestation in thyrotoxicosis?
No
Acropachy will most likely happen in which types of patients?
Pts with opthamopathy and thyroid dermopathy. (If these two aren’t present but acropachy is, these two can come on secondarily).
Patients with thyroid disease that smoke.
Involuntary muscle contraction
Tetany
In hyperthyroidism, what is the most common cause of tetany (though rare)?
Hypomagnesemia as a result of increased renal excretion of magnesium.
Tetany in hyperthyroidism can result in _______.
Hypocalcemia
