Importance of Feedback regulation through HPT Axis Flashcards
What are the main symptoms of hyperthyroidism?
Heat intolerance, weight loss, pounding heart, difficulty sleeping, anxiety/restlessness, hand tremors.
Describe the mechanism of action for thyroid hormones.
T4 and T3 are taken up by cells; T4 is converted intracellularly into T3, which binds to nuclear receptors and activates gene transcription.
What are the biological effects of thyroid hormones?
Brain development (perinatal period), growth via effect on GH production, thermogenic action (heat production), and synthesis and effects of GH.
What is Graves’ disease and how is it diagnosed?
Graves’ disease is the most common form of hyperthyroidism, characterized by high free T4 and low TSH levels. It is caused by thyroid autoantibodies that stimulate the TSH receptors.
Why is free T3 not routinely tested?
T3 is less stable and its levels vary in different tissues. It is more useful in diagnosing hyperthyroidism but not routinely tested due to its variability.
What are the symptoms and diagnostic markers for hypothyroidism in adults?
Symptoms include cold intolerance, slow heart rate, constipation, fatigue, and goiter. Diagnostic markers are low free T4 and high TSH levels.
What are the roles of TRH and TSH in the regulation of thyroid hormones?
TRH from the hypothalamus stimulates the anterior pituitary to release TSH, which in turn stimulates the thyroid gland to produce free T3 and T4.
What condition is characterized by low free T4 and high TSH levels?
Primary hypothyroidism, often due to Hashimoto’s thyroiditis.
Explain the significance of maternal thyroid hormone transfer during pregnancy.
Maternal thyroid hormone is crucial for fetal brain development until the fetus can produce its own thyroid hormone from 12 weeks gestation.
How is a thyrotropin-secreting tumor diagnosed?
Through serum thyrotropin and free T4 measurements, showing normal or increased free T4 levels with measurable thyrotropin.
