Hyperthrodisum Flashcards
- What do the paraventricular nuclei inside the hypothalamus secrete?
Thyrotropin-releasing hormone (TRH).
- Where does TRH go after secretion, and what cells does it stimulate?
TRH goes into the hypophyseal portal system and stimulates thyrotropes in the adenohypophysis.
- What is the role of TSH in the thyroid gland?
TSH binds to receptors (TSH-R) on the follicles, stimulating the production of thyroglobulin and iodine incorporation.
How is iodinated thyroglobulin produced?
TSH-R stimulates thyroid peroxidase,
converting iodide to iodine and
combining it with thyroglobulin.
What happens after iodinated thyroglobulin is endocytosed back into the follicular cell?
Proteases cleave thyroid hormone (T3 and T4) from iodinated thyroglobulin, releasing it into the blood.
- How does thyroid hormone enter cells, and what is the fate of T4 inside cells?
Thyroid hormone diffuses across cell membranes. The majority of T4 is converted to T3 by deiodinases.
- What are the general effects of thyroid hormone on all cells?
2 a-d
Increases sodium-potassium ATPases, stimulates glycogenolysis, glycolysis, lipolysis, and modifies cellular activity.
What cellular activities are stimulated by thyroid hormone in all cells?
number2a-d
Increases sodium-potassium ATPases, stimulates glycogenolysis, glycolysis, and lipolysis.
(3) What effects does thyroid hormone have on the liver?
Stimulates LDL uptake and regulates the production of steroid hormone binding globulins, e.g., thyroxine binding globulin.
(4) How does thyroid hormone influence the heart?
Increases beta-receptor sensitivity, leading to an increase in heart rate and contractility. Maintains vasomotor tone.
(5) What role does thyroid hormone play in bones?
Maintains the balance between bone resorption via osteoclasts and bone deposition via osteoblasts.
(6) How does thyroid hormone affect the brain?
Increases sympathetic nervous system activity.
(7) What changes does thyroid hormone induce in the GI tract?
6
Increases GI motility and GI secretions.
- What effects does thyroid hormone have on skeletal muscles?
Maintains normal muscle contraction, stimulates muscle development and regeneration, and maintains calcium ATPases on the sarcoplasmic reticulum.
- How does thyroid hormone affect the integumentary system?
Maintains good blood flow to skin, hair, and nails,
stimulates growth, and
maintains blood flow to sebaceous glands and eccrine sweat glands,
stimulating secretions.
- What role does thyroid hormone play in fibroblasts?
Maintains the production of glycosaminoglycan and
other extracellular proteins.
What are the effects of thyroid hormone on skeletal muscles?
Maintains
normal muscle contraction,
stimulates muscle development and regeneration, and maintains calcium ATPases on the sarcoplasmic reticulum.
How does thyroid hormone influence the integumentary system?
Maintains good blood flow to skin, hair, and nails, stimulates growth, and maintains blood flow to sebaceous glands and eccrine sweat glands, stimulating secretions.
What is the role of thyroid hormone in fibroblasts?
Maintains the production of glycosaminoglycan and other extracellular proteins.
- What happens when thyroid hormone leaks out of injured cells?
Causes transient hyperthyroidism, often followed by hypothyroidism.
- What are the causes of destruction of the thyroid gland?
(i) Hashimoto thyroiditis, (ii) Postpartum thyroiditis, (iii) Subacute granulomatous thyroiditis, (iv) Drug-induced thyroiditis, (v) Iodine-induced thyroiditis.
What are the causes of primary secondary hyperfunction of the thyroid gland?
(i) Graves’ disease, (ii) Toxic adenoma or toxic multinodular goiter (TMG),
2nd
(iii) Pituitary adenoma, (iv) Increased beta-hCG production.
(1) What are the metabolic effects of excess thyroid hormone?
Increased metabolism, weight loss, increased appetite, elevated body temperature.
How does excess thyroid hormone affect sodium-potassium ATPase activity?
Increases ATP demand.
What are the effects of excess thyroid hormone on glycogenolysis and glycolysis?
Increases glycogenolysis (breakdown of glycogen into glucose) and glycolysis (breakdown of glucose into pyruvate).
What is the impact of excess thyroid hormone on lipolysis?
Increases lipolysis (breakdown of lipids into fatty acids and glycerol).
(2) How does excess thyroid hormone affect the heart?
Increases beta-receptor sensitivity, ->
heart rate, and
contractility, leading to tachycardia,
increased stroke volume, and hypertension.
(3) What effects does excess thyroid hormone have on bones?
Increases osteoclast activity,
leading to increased bone resorption and an
elevated risk of osteoporosis and fractures.
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(4) How does excess thyroid hormone influence the brain?
Increases sympathetic nervous system activity, causing anxiety, restlessness, agitation, and features like lid lag and retraction.
(5) What changes occur in the GI tract due to excess thyroid hormone?
Increases GI motilityand secretions, leading to diarrhea.
(6) What effects does excess thyroid hormone have on skeletal muscles?
Increases muscle contractions and growth, potentially causing myopathy (muscle pain without damagethus NORMAL CK ).
(7) How does excess thyroid hormone affect the integumentary system?
Increases blood flow to skin, hair, and nails, resulting in thick and coarse hair, flushed skin, thicker nails with onycholysis, and increased sweating and sebum production.
(8) What changes occur in the liver due to excess thyroid hormone?
Increases the number of LDL receptors,leading to increased LDL uptake, and
enhances the production of steroid hormone binding globulins, including thyroxine binding globulin and sex hormone binding globulins.
(9) What clinical features are associated with fibroblasts in Graves’ disease?
TSH receptor antibodies can activate fibroblasts in the dermis, causing glycosaminoglycan accumulationalong with water , known as
pretibial myxedema. TSH receptor antibodies can also activate T-cells, leading to
exophthalmos.
- How does Graves’ disease affect fibroblasts in the dermis?
TSH receptor antibodies in Graves’ disease can directly activate fibroblasts in the dermis, leading to glycosaminoglycan accumulation and pretibial myxedema.
(1) How is primary and secondary hyperthyroidism differentiated?
Both show increased free T4 levels, but the key is TSH levels vary. Increased TSH suggests pituitary adenoma, while
decreased TSH may indicate excess ß-hCG, requiring further investigation.
When is a ß-hCG check necessary in the diagnosis of hyperthyroidism?
If the patient is pregnant or excess ß-hCG is suspected.
(2) How is the cause of primary hyperthyroidism differentiated?
Thyroid exam with palpation for nodules is performed. Nodules may require further testing, such as a radioactive iodine uptake scan (first line) or ultrasound with doppler (second line). The uptake scan helps determine if the nodule is hot (benign), cold (likely malignant), or associated with Graves’ disease, toxic adenoma, or toxic multinodular goiter. No uptake or low uptake may indicate thyroiditis or exogenous use.
What further evaluation is needed for no uptake or low uptake hyperthyroidism?
Anti-thyroid antibodies, including TSH receptor antibodies (indicative of Graves’ disease) and anti-TPO antibodies (suggestive of Hashimoto thyroiditis or postpartum thyroiditis). Serum thyroglobulin levels can also help differentiate causes, with elevated levels indicating follicular cell injury and potential causes including thyroiditis, struma ovarii (confirmed with ultrasound and biopsy), and decreased levels suggesting exogenous thyroid use.
(1) What is the symptomatic treatment for hyperthyroidism?
Symptomatic treatment involves the use of beta blockers, such as propranolol, which decreases T4 →T3 conversion in target cells, rendering thyroid hormone ineffective.
How does propranolol contribute to the symptomatic treatment of hyperthyroidism?
Propranolol decreases T4 →T3 conversion in target cells, making thyroid hormone ineffective.
(2) What are the anti-thyroid medications used for hyperthyroidism?
Methimazole (first line) and propylthiouracil decrease T4 →T3 conversion in target cells, rendering thyroid hormone ineffective. Propylthiouracil also inhibits thyroid peroxidase from iodinating thyroglobulin, preventing the production of functional thyroid hormone. Radioactive iodine ablation is used when other measures fail and involves the destruction of hyperfunctioning thyroid follicles with iodine-131.
How does radioactive iodine ablation work in the treatment of hyperthyroidism?
Iodine-131 is taken up by hyperfunctioning thyroid follicles, generating gamma waves that destroy the follicles, rendering them ineffective at synthesizing and producing thyroid hormone.
(3) When is surgery indicated in the treatment of hyperthyroidism?
Surgery is indicated for large goiters with surrounding compression, severe Graves’ with ophthalmopathy, and refractory hyperthyroidism with associated complications. Lobectomy or total thyroidectomy may be performed, with contraindications including pregnancy.
What are the indications and contraindications for thyroid surgery?
Indications include large goiters with surrounding compression, severe Graves’ with ophthalmopathy, and refractory hyperthyroidism with associated complications. Contraindications include pregnancy.
(1) What are some causes of thyrotoxicosis (thyroid storm)?
Causes include infection (sepsis), DKA, myocardial infarction, surgery, and trauma.