HD - thyroid basics - Flashcards in University Medicine

What natural events leads to an enlarged trachea?

Pregnancy, adolescence, lactation and the later portion of the menstrual cycle

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What is the blood supply of the thyroid?

Sup. And inf. thyroid arteries, originating from the external carotid and subclavian

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What gland is found within the thyroid gland and what is it’s role?

Parathyroid gland involved in ca2+ metabolism

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What are the products of the thyroid gland? (3)

T3, T4, calcitonin (parafollicular of c-cells)

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How many tyrosine residues are in glycoprotein thyroglobulin?

115 (only 15-20 act as a substrate for iodine)

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Iodine is organified in the thyroid by what enzyme? In the prescence of what?

Thyroid peroxidase in the presence of H2O2

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MIT =

Monoiodotyrosine

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In a normal thyroid state is more T4 or T3 produced?

T4

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Synthesis of T4 and T3 from hypothalamus to periphery?

Hypothalamus releases TRH (3aa) acts on thyrotrophs in the ant. Pituitary to release TSH and thyrotropin. TSH stimulates the thyroid to release T4 and T3, T4 is converted to T3 in the periphery.

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Is T3 or T4 more potent on T4 receptors?

T3

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What acts on thyrotrophs to decrease TSH release?

T3

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Where is thyroglobulin stored?

In colloids

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How much more T4 is found in plasma than T3

50x, 5-fold

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Thyroid hormones interact with what type of receptors?

Nuclear receptors

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Explain the mechanism of T3 entering the cell to the final effect produced?

T3 enters the nucleus and binds to thyroid receptor to form a diner, the hormone receptor complex then binds to thyroid HRE on DNA and takes 4-5hrs for the effect to take place

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What is the main cause of hypothyroidism?

The autoimmune disease Hashimoto’s thyrotoxicosis

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What is hashimoto’s thyrotoxicosis?

An Ab to thyroglobulin or thyroperoxidase

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How can you treat hypothyroidism?

Thyroxine, liothyronine (Na salt of T3 - in severe cases where a more rapid response is required)

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What causes non-toxic goitre?

Iodine deficiency

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What is the daily requirement of iodine and what is the level for deficiency?

150micrograms/day, deficiency = <50

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Definition of goitrogen?

Something that suppresses hormone secretion, increasing TSH

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What is more common, hypo or hyperthyroidism?

Hyperthyroidism

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What is grave’s disease?

TSAb producing prolonged stimulation of TSH

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What are the features of grave’s? (5)

Thyrotoxicosis, goitre, exophthalmos and upper lid retraction, peritibial myxoedema

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Treatment of hyperthyroidism?

Anti-thyroid drugs (carbimazole - converted to methimazole in the body), propylthiouracil (inhibits thyroid peroxidase and conversion of T4 to T3), propranolol (blocks the SNS effects of hormones), radioiodine, surgery (LUGOLs)

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HD - thyroid basics

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