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.