Endocrinology- Thyroid Flashcards
A 23-year-old student presents with a 4 month history of
sweating, palpitations, anxiety, tremor and weight loss despite
a good appetite.
On examination she is fidgety, has warm sweaty palms with a
marked tremor, staring eyes and a goitre.
You suspect hyperthyroidism.
What is hyperthyroidism?
A condition where the thyroid gland produces excessive amounts of thyroid hormones, leading to an accelerated metabolism.
What are common causes of hyperthyroidism?
Graves’ disease, toxic nodular goiter, thyroiditis, and excessive iodine intake.
What are the symptoms of hyperthyroidism?
Weight loss, increased appetite, rapid heart rate, anxiety, tremors, heat intolerance, and excessive sweating.
How is hyperthyroidism diagnosed?
Through blood tests measuring levels of TSH (thyroid-stimulating hormone) and free T4 (thyroxine), and sometimes radioactive iodine uptake tests.
What are the treatment options for hyperthyroidism?
Antithyroid medications (e.g., methimazole), radioactive iodine therapy, and sometimes thyroidectomy.
What is hypothyroidism?
A condition where the thyroid gland does not produce enough thyroid hormones, leading to a slowed metabolism.
What are common causes of hypothyroidism?
Hashimoto’s thyroiditis, iodine deficiency, certain medications, and thyroid surgery.
What are the symptoms of hypothyroidism?
Fatigue, weight gain, cold intolerance, dry skin, hair loss, constipation, and depression.
How is hypothyroidism diagnosed?
Through blood tests measuring TSH and free T4 levels.
What are the treatment options for hypothyroidism?
Thyroid hormone replacement therapy, typically with levothyroxine.
Causes of hyperthyroidism
Graves Disease
Toxic Multinodular goitre
Toxic nodule
Thyroiditis
Iodine-induced
Thyrotoxicosis factitia
TSH-secreting pituitary tumour
Trophoblastic Disease
Struma Ovarii
What is Graves’ disease?
An autoimmune disorder that causes hyperthyroidism, characterized by the overproduction of thyroid hormones.
What causes Graves’ disease?
The immune system produces antibodies (anti- TSH receptor antibodies) that stimulate the thyroid gland, leading to excessive hormone production.
What are the common symptoms of Graves’ disease?
Weight loss, rapid heartbeat, anxiety, heat intolerance, increased sweating, tremors, goiter (enlarged thyroid), and bulging eyes (exophthalmos), pretibial myxoedema, thyroid acropachy
How is Graves’ disease diagnosed?
Through blood tests that measure levels of TSH, free T4, and the presence of TSH receptor antibodies. Imaging studies like thyroid scans may also be used.
What complications can arise from untreated Graves’ disease?
Complications include heart problems (like atrial fibrillation), osteoporosis, and a life-threatening condition called thyroid storm.
What are the treatment options for Graves’ disease?
Treatment options include antithyroid medications (like methimazole, Thionamides,
Propylthiouracil
), radioactive iodine therapy, and sometimes surgery (thyroidectomy).
How does Graves’ disease affect the eyes?
It can cause Graves’ ophthalmopathy, leading to symptoms like bulging eyes, dryness, irritation, and vision problems due to inflammation of the eye muscles and surrounding tissues.
What lifestyle changes can help manage Graves’ disease?
Regular monitoring of thyroid levels, a balanced diet, stress management techniques, and avoiding stimulants like caffeine can help.
What is the Hypothalamic-Pituitary-Thyroid (HPT) axis?
A complex system that regulates thyroid hormone production through interactions between the hypothalamus, pituitary gland, and thyroid gland.
What role does the hypothalamus play in the HPT axis?
The hypothalamus releases thyrotropin-releasing hormone (TRH), which stimulates the anterior pituitary to produce thyroid-stimulating hormone (TSH).
What is the function of thyroid-stimulating hormone (TSH)?
TSH stimulates the thyroid gland to produce and release thyroid hormones (T3 and T4), which regulate metabolism.
How do thyroid hormones (T3 and T4) influence the body?
They regulate metabolic processes, including energy production, growth, development, and body temperature.
What feedback mechanism exists within the HPT axis?
Negative feedback: high levels of T3 and T4 inhibit the release of TRH from the hypothalamus and TSH from the pituitary, maintaining hormone balance.
What can disrupt the HPT axis?
Conditions like hypothyroidism, hyperthyroidism, pituitary disorders, and hypothalamic damage can disrupt normal functioning.
How is the HPT axis assessed clinically?
Through blood tests measuring TRH, TSH, T3, and T4 levels, which help diagnose thyroid disorders.
What is the relationship between T3 and T4?
T4 (thyroxine) is the primary hormone produced by the thyroid, which is converted into the more active T3 (triiodothyronine) in peripheral tissues.
What are the main thyroid function tests?
The main tests include TSH (thyroid-stimulating hormone), free T4 (thyroxine), and free T3 (triiodothyronine).
What does an elevated TSH level indicate?
An elevated TSH level typically suggests hypothyroidism, as the pituitary gland produces more TSH to stimulate a sluggish thyroid.
What does a low TSH level suggest?
A low TSH level usually indicates hyperthyroidism, where the thyroid gland is overactive, leading to reduced TSH production.
How do free T4 levels assist in diagnosing thyroid conditions?
Free T4 levels help determine thyroid function: elevated levels indicate hyperthyroidism, while low levels indicate hypothyroidism.
What role does free T3 play in thyroid function tests?
Free T3 is particularly important in diagnosing hyperthyroidism and assessing the severity of thyroid hormone activity, especially in cases of T3 toxicosis.
What does it mean if TSH is normal but free T4 is low?
This situation may indicate subclinical hypothyroidism or central hypothyroidism (pituitary or hypothalamic dysfunction).
What is the significance of thyroid autoantibodies in testing?
The presence of thyroid autoantibodies (like TPOAb or TSHRAb) can indicate autoimmune thyroid disease, such as Hashimoto’s thyroiditis or Graves’ disease.
How do thyroid function test results vary in pregnancy?
During pregnancy, TSH levels may decrease, and reference ranges for T4 and T3 may change, requiring careful interpretation.
What should be considered when interpreting thyroid function tests in the elderly?
In older adults, TSH levels may be higher, and they may present with atypical symptoms, making interpretation more complex.
What is primary hypothyroidism?
A condition where the thyroid gland is underactive and fails to produce enough thyroid hormones.
What are the typical findings in primary hypothyroidism?
Elevated TSH levels, low free T4 levels, and possible high free T3 levels if there’s a compensatory response.
What is secondary hypothyroidism?
A condition caused by insufficient stimulation of the thyroid gland due to inadequate TSH secretion from the pituitary gland.
What are the typical findings in secondary hypothyroidism?
Low TSH levels, low free T4 levels, and low free T3 levels.
What is subclinical hypothyroidism?
A mild form of hypothyroidism where TSH is elevated, but free T4 levels remain normal.
What are the typical findings in subclinical hypothyroidism?
Elevated TSH levels, normal free T4, and free T3 levels.
What is sick euthyroid syndrome?
A condition in which thyroid function tests are abnormal in the presence of a non-thyroidal illness, but the thyroid gland itself is functioning normally.
What are the typical findings in sick euthyroid syndrome?
Low T3 levels, normal TSH, and free T4 levels may be low or normal.
What is a TSHoma?
A rare pituitary tumor that secretes TSH, leading to increased stimulation of the thyroid gland.
What are the typical findings in TSHoma?
Elevated TSH levels, elevated free T4 and free T3 levels.
What is hyperthyroidism?
A condition characterized by the overproduction of thyroid hormones, leading to an accelerated metabolism.
What are the typical findings in hyperthyroidism?
Low TSH levels, elevated free T4 levels, and elevated free T3 levels.
What are the findings in sick euthyroid syndrome during recovery?
As the underlying illness improves, T3 levels may rise, TSH levels normalize, and free T4 levels typically return to normal.
What is Neomercazole?
Neomercazole, or methimazole, is an antithyroid medication used to treat hyperthyroidism by inhibiting the production of thyroid hormones.
How does Neomercazole work?
It inhibits thyroid peroxidase, blocking the iodination of tyrosine residues and preventing the synthesis of T3 and T4 hormones.
What are the common indications for Neomercazole?
It is primarily used to treat Graves’ disease, toxic nodular goiter, and as preparation for thyroid surgery or radioactive iodine treatment.
What are the potential side effects of Neomercazole?
Common side effects include rash, arthralgia, nausea, and gastrointestinal disturbances. Serious side effects can include agranulocytosis and liver toxicity, thrombocytopenia, lupus like syndrome
How should Neomercazole be monitored during treatment?
Regular monitoring of thyroid function tests (TSH, free T4) and complete blood counts to check for agranulocytosis is recommended.
What precautions should be taken while using Neomercazole?
Patients should be monitored for signs of infection (due to agranulocytosis), liver function, and any signs of allergic reactions.
Can Neomercazole be used during pregnancy?
Methimazole can be used during pregnancy, but it should be prescribed at the lowest effective dose, particularly in the first trimester, due to potential teratogenic effects.
What is agranulocytosis?
A rare condition (0.3–1%) characterized by a significantly reduced white blood cell count, increasing the risk of infections.
When does agranulocytosis typically occur during treatment?
It usually occurs within the first few weeks to months of starting treatment with Neomercazole or PTU.
What are the common symptoms of agranulocytosis?
Symptoms include fever and sore throat, which may indicate an infection.
What should be done if agranulocytosis is suspected?
Check the white cell count (WCC) for any evidence of infection, and stop Neomercazole or PTU immediately if agranulocytosis is confirmed.
Check the white cell count (WCC) for any evidence of infection, and stop Neomercazole or PTU immediately if agranulocytosis is confirmed.
Treatment may include antibiotics to manage infections and granulocyte-macrophage colony-stimulating factor (GM-CSF) to stimulate white blood cell production.
What is hepatotoxicity?
A rare condition (0.3–1%) where liver function is impaired due to medication use, particularly with Neomercazole or PTU.
When does hepatotoxicity typically occur during treatment?
It usually occurs within the first few weeks to months of starting treatment.
What are the common symptoms of hepatotoxicity?
Symptoms may include fever and sore throat, similar to agranulocytosis.
What should be done if hepatotoxicity is suspected?
Stop Neomercazole or PTU immediately if liver dysfunction is confirmed.
How should patients be managed if they develop hepatotoxicity?
Monitor liver function tests closely and consider the use of supportive care and antibiotics if needed.
What are antithyroid drugs?
Medications used to decrease the production of thyroid hormones in conditions like hyperthyroidism.
What is Neomercazole?
An antithyroid medication that inhibits thyroid hormone synthesis by blocking thyroid peroxidase
What is Lugol’s iodine?
A solution of potassium iodide and iodine used to reduce thyroid hormone release and vascularity before surgery.
How does Lugol’s iodine work?
It decreases thyroid hormone synthesis and temporarily inhibits hormone release by saturating the thyroid gland with iodine.
What is the role of β-blockers in hyperthyroidism?
They help manage symptoms such as tachycardia, anxiety, and tremors by blocking adrenergic receptors.
Which β-blockers are commonly used?
Propranolol and atenolol are commonly used in hyperthyroid patients.
How is lithium used in hyperthyroidism?
Lithium can reduce the release of thyroid hormones by inhibiting the thyroid gland’s response to TSH.
What is cholestyramine?
A bile acid sequestrant that can be used to help reduce thyroid hormone levels in the gut by binding to hormones.
When is cholestyramine indicated?
It is used in cases of severe hyperthyroidism or thyrotoxic crisis to rapidly decrease circulating thyroid hormone levels.
What is the role of dexamethasone in hyperthyroidism?
A corticosteroid that can decrease peripheral conversion of T4 to T3 and reduce inflammation in thyroiditis.
When is dexamethasone indicated?
It is often used in thyrotoxic crisis or severe cases of hyperthyroidism.
Common hyperthyroidism diseases
Graves Dx
Multinodular Goiter (MNG)
Thyroidistis
Solitary nodule
What is Graves’ disease?
An autoimmune disorder that causes hyperthyroidism due to the overproduction of thyroid hormones.
Rx: Neomercazole
What are the key features of Graves’ disease?
Symptoms include weight loss, rapid heartbeat, anxiety, heat intolerance, goiter, and exophthalmos (bulging eyes).
What is multinodular goiter (MNG)?
A condition where multiple nodules develop in the thyroid gland, leading to increased hormone production.
Rx: I 131
What are the symptoms of MNG?
Symptoms may include neck swelling, difficulty swallowing or breathing, and symptoms of hyperthyroidism.
What is thyroiditis?
Inflammation of the thyroid gland, which can lead to both hyperthyroidism (in the early phase) and hypothyroidism.
Rx; Usually nil
- Steorids
-NSAIDS
What types of thyroiditis can cause hyperthyroidism?
Subacute (De Quervain’s) thyroiditis and postpartum thyroiditis can cause transient hyperthyroid symptoms.
What is a solitary thyroid nodule?
A single abnormal growth within the thyroid gland that can be either benign or malignant.
Rx: surgery or I 131
Can a solitary nodule cause hyperthyroidism?
Yes, if the nodule is functioning (producing thyroid hormones), it can lead to hyperthyroidism, known as toxic adenoma.
Iodine 131
A radioactive isotope of iodine used primarily in the treatment of hyperthyroidism and certain types of thyroid cancer.
I-131 is taken up by the thyroid gland, where its radioactive decay destroys thyroid tissue, reducing hormone production.
Primary causes of hypothyroidism
Post surgery / 131I
Hashimotos thyroiditis
Antithyroid drugs
Secondary causes of hypothyroidism
Hypothalamic-pituitary disease
What is Levothyroxine?
Levothyroxine is a synthetic form of thyroxine (T4) used to treat hypothyroidism.
What are some brand names for Levothyroxine?
Common brand names include Eltroxin and Euthyrox.
What is the half-life of Levothyroxine?
The half-life of Levothyroxine is approximately 7 days.
How long does it take to reach a steady state with Levothyroxine?
It takes about 5-6 half-lives (approximately 6-8 weeks) to reach a steady state, so this period is needed before assessing its effects on hormone levels.
What is the initial dosage of Levothyroxine?
The initial dosage is typically 1.4 to 1.6 µg/kg of ideal body weight.
What factors influence the initial dosage of Levothyroxine?
Dosage depends on the degree of hypothyroidism, patient age, and overall health status.
What is the recommended starting dose for elderly patients or those with ischemic heart disease (IHD)?
The starting dose for elderly patients or those with IHD is usually 25 µg/day.
How is Levothyroxine monitored during treatment?
Patients should have regular thyroid function tests (TSH, free T4) to ensure appropriate dosing and effectiveness.
How should therapy with Levothyroxine be monitored?
Therapy should be monitored primarily by measuring TSH levels.
What should be considered when interpreting TSH results?
Normal TSH ranges can vary according to the specific assay used, so it’s important to refer to the normal range provided by the laboratory.
When is the best time to take Levothyroxine?
Levothyroxine should be taken on an empty stomach, ideally 30-60 minutes before breakfast.
What should patients be cautious about regarding Levothyroxine absorption?
Patients should be aware that certain medications and supplements can decrease the absorption of thyroid hormones.
Which types of medications may interfere with Levothyroxine absorption?
Medications such as calcium supplements, iron supplements, and certain antacids can interfere with Levothyroxine absorption.
How should Levothyroxine be taken if patients are on medications that affect absorption?
It is generally advised to separate the doses of Levothyroxine and any interacting medications by at least 2-3 hours.
Drugs affecting the absorption of thyroid hormone
Cholestyramine
Calcium carbonate
PPI’s (omeprazole, lansoprazole)
Raloxifene, ciprofloxacin
Sucralfate, ferrous sulfate, aluminium hydroxide
Chromium
27 year old woman
Tired, gaining weight, constipated
TSH 15.3 mIU/L (0.37-3.5)
T4 6.4 pmol/L (7.2-16.4)
Primary Hypothyroidism
27 year old woman
Tired, gaining weight, constipated
TSH 7.3 mIU/L (0.37-3.5)
T4 12.4 pmol/L (7.2-16.4)
Subclinical Hypothyroidism
27 year old woman
Tired, gaining weight, constipated
TSH 2.3 mIU/L (0.37-3.5)
T4 6.5 pmol/L (7.2-16.4)
Likely Central (Secondary) Hypothyroidism or Thyroid Hormone Deficiency.
27 year old woman
Tired, gaining weight, constipated
TSH 1.3 mIU/L (0.37-3.5)
T4 12.4 pmol/L (7.2-16.4)
normal
A 46-year old woman presented complaining of fatigue. There were significant findings on examination and initial bloods done were normal.
There after her thyroid function was done. Results of which are shown below:
serum tsh 12.5 (0.35- 5.5.)
serum free T4 7.5 (11.5- 22.7)
What is the most appropriate management?
A. Carbimazole
B. Lugol’s iodine
C. Radioactive iodine
D. Levothyroxine
D. Levothyroxine
What is the commonest cause of hypothyroidism in South Africa?
A. Iatrogenic
B. Autoimmune thyroiditis
C. Iodine deficiency
D. Pituitary disease
B. Autoimmune thyroiditis
A 37-year old woman presents with weight loss and excessive sweating. Her husband reports that recently she is very anxious and you notice a fine tremor. Her pulse rate is 96 beats per minute. A large, non-tender goitre us noted. Examination of her eyes is unremarkable with no evidence of exophthalmos.
Her blood results are as follows:
serum tsh 0.12 (0.35- 5.5.)
serum free T4 35 (11.5- 22.7)
What is the most likely diagnosis?
A. Hashimoto’s thyroiditis
B. Toxic multinodular goitre
C. Grave’s disease
D. T3 secreting adenoma
C. Grave’s disease
What is the mechanism of action of neomercazole?
A. Suppression of pituitary gland
B. Prevents release of T4
C. Competitive inhibition of TSH receptors
D. Inhibits thyroid perioxidase
D. Inhibits thyroid perioxidase
A 34-year-old woman presents complaining of fatigue and cold intolerance. Her thyroid function is shown below:
Laboratory test Value Normal range
Serum TSH 8.8 0.35 – 5.5 mIU/l
Serum free T4 13 11.5 – 22.7 pmol/l
How would you manage this patient further?
A. Check anti-thyroid antibodies
B. Start low dose levothyroxine
C. Repeat TSH in 3-6 months
D. Repeat TSH in 6-8 weeks
A. Check anti-thyroid antibodies
Which of the following is a side effect of neomercazole?
A. Agranulocytosis
B. Thrombosis
C. Thrombocytosis
D. Anaemia
A. Agranulocytosis
A 65-year-old woman presents with palpitations and fatigue. On examination she has sinus tachycardia with a smooth diffuse goitre and proptosis.
What is the most likely diagnosis?
A. Thyroid malignancy
B. Toxic multinodular goitre
C. Grave’s Disease
D. Toxic nodule
C. Grave’s Disease
Where is T3 predominantly formed?
A. Pituitary gland
B. Peripheral conversion of T4
C. Thyroid gland
D. Hypothalamus
B. Peripheral conversion of T4
A 24-year old woman presents complaining of a tremor, palpitations and anxiety. On examination she has an exquisitely tender thyroid and a reduced thyroid uptake scan.
What is the most likely diagnosis?
A. Grave’s disease
B. Single toxic nodule
C. Thyroiditis
D. Multi-nodular toxic goitre
C. Thyroiditis
In a patient with hypothyroidism who is started on levothyroxine, after what period should response be reviewed?
A. 3-6 weeks
B. 8-12 weeks
C. 6-8 weeks
D. 3 days
C. 6-8 weeks
What is the initial screening test for thyroid function?
A. TSH
B. Free T3
C. Free T4
D. Thyroid antibodies
A. TSH
What is the interpretation of the following thyroid function?
Laboratory test Value Normal range
Serum TSH 6 0.35 – 5.5 mIU/l
Serum free T4 8 11.5 – 22.7 pmol/l
A. Secondary hyperthyroidism
B. Subclinical hypothyroidism
C. Sick euthyroid syndrome
D. Primary hypothyroidism
D. Primary hypothyroidism
Which of the following signs is NOT pathognomonic for Grave’s Disease?
A. Pretibial myxoedema
B. Tremor
C. Proptosis
D. Acropachy
B. Tremor
A 33-year-old woman presents with palpitations, heat intolerance and weight-loss. On examination her blood pressure is 140/80mmHg with a heart rate of 100 beats/minute. Of note she has bilateral swelling over the tibia with skin discoloration.
Her blood results are as follows:
Serum TSH: 0.12 (0.35- 5.5)
Serum free T4: 35 (11.5- 22.7)
What is the most likely diagnosis?
A. Thyroid adenoma
B. De Quervain’s thyroiditis
C. Struma Ovari
D. Grave’s Disease
D. Grave’s Disease
In a patient with hyperthyroidism, which of the following eye signs is NOT considered to be a feature of Grave’s Eye Disease?
A. Chemosis
B. Lid lag
C. Proptosis
D. Periorbital puffiness
B. Lid lag
What is the commonest cause of hyperthyroidism?
A. Single toxic nodule
B. Thyroid Cancer
C. Toxic multi-nodular goitre
D. Grave’s Disease
D. Grave’s Disease
What is the interpretation of the following thyroid function?
Laboratory test Value Normal range
Serum TSH 8 0.35 – 5.5 mIU/l
Serum free T4 13 11.5 – 22.7 pmol/l
A. Secondary hypothyroidism
B. Sick Euthyroid syndrome
C. Subclinical hypothyroidism
D. Primary hypothyroidism
C. Subclinical hypothyroidism
What is the interpretation of the following thyroid function?
Laboratory test Value Normal range
Serum TSH 0.01 0.35 – 5.5 mIU/l
Serum free T4 35 11.5 – 22.7 pmol/l
A. Subclinical hyperthyroidism
B. Sick euthyroid syndrome
C. Primary hyperthyroidism
D. Secondary hyperthyroidism
C. Primary hyperthyroidism
A 58-year-old woman presents with confusion. On examination she is pyrexial, tachycardic and hypotensive. A diagnosis of thyroid storm is made.
Which of the following is the best management for this patient?
A. Adrenalin, carbimazole, hydrocortisone
B. Adrenaline, hydrocortisone, beta-blocker
C. Beta blocker, carbimazole, hydrocortisone
D. Beta blocker, carbimazole, Adrenaline
C. Beta blocker, carbimazole, hydrocortisone
When treating patients with hypothyroidism what blood test is used to assess adequacy of treatment?
A. Total T4
B. TSH
C. Free T3
D. Free T4
B. TSH
