Thyroid Hormones

Muscle Force

A slight increase in Thyroid Hormone results in an increase in _____

Iodide Trapping

Ability of the basal membrane of the Thyroid Cell to actively pump the iodide to the interior of the cell

Inhibits the pituitary from forming TSH and inhibits Growth Hormone

After thermal/caloric signals are received and the hypothalamus releases TRH to make the Anterior Pituitary release TSH, TSH causes thyroid gland to secrete T3 and T4 and then signals the hypothalamus to secrete SOMATOSTATIN, which:

Latency Period

Amount of time it takes a hormone to respond

Lysosomes

Break down thyroglobulin to release the T3 and T4 so they are free to diffuse in the cell

Thyroid Hormone-Binding Globulin (~70%), Pre-Albumin (15%), Albumin (15%)

Carrier proteins that Thyroid hormones attach to:

Excitability/Nervousness, Muscle weakness, fatigue, diarrhea, weight loss, Tremors of hands, Increased sweating, Exophthalmos (eyeball pertrustion)

Characteristics of Hyperthyroidism

Low Heart Rate and Blood Volume, Muscle weakness/fatigue, Long sleep, constipation, mental sluggishness, Atherosclerosis, Myxedema (excessive tissue gel, occurs with total lack of thyroid function), Weight Gain

Characteristics of Hypothyroidism

Hypothyroidism

Condition that has sleepiness as a characteristic trait

Hyperthyroidism

Condition that results in tiredness but difficulty sleeping

Goiter

Deficiency of iodine in the diet causes the thyroid gland to enlarge, which is called

Hyperthyroidism

Disorder marked by excessive secretion of thyroid hormone due to thyroid-stimulating immunoglobins that activate the cAMP system. Treated by surgical removal of gland or radioactive iodine administration to destroy cells

Hypothyroidism

Disorder marked by low levels of thyroid hormone in the circulation. Treated by replacement/ supplemental therapy with thyroid hormone

Colloid Droplets

During the formation of T3 and T4, the entire molecule is transported back into the cell via endocytosis into ________

Basal Metabolic Rate

Excessive amounts of thyroid hormone can cause an increase in _____ of 60-100%

Cretinism

Extreme hypothyroidism results in _____, which leads to inhibited skeletal growth and disproportionate growth of soft tissue

Iodine

Extremely important element for normal thyroid activity

Transfer of iodides from the blood into the thyroid glandular cells, and hence into the follicle

First stage in the formation of thyroid hormones is the:

Thyroid Gland

Gland located just below the larynx on either side, anterior to the trachea

TSH

Hormone released by the hypothalamus that plays a major role in regulating these thyroid hormones & increasing thyroid glandular cell activities

Weight Loss

Increased thyroid hormone almost always causes _______

Oxidized by peroxide

Iodide taken up by the thyroid gland is ______ in the lumen of the follicle

Sexual Dysfunction

Lack of Thyroid Hormone can lead to ______

Thyroglobulin

Large glycoprotein made by the epithelial cuboidal cells lining the follicle that is released into the colloid space. Helps make T3 & T4; VERY slow reabsorption back through the follicular epithelim

cAMP System

Plays a major role as a 2nd messenger in the thyroid gland by activating protein kinase and phosphorylating the protein to secrete Thyroglobulin

Iodinase

Responsible for accelerating the reaction of iodine binding to tyrosine residues and results in one of two products: Monoiodotyrosine (MIT) or Diiodotyrosine (DIT)

Increased Thyroglobulin production, Increased iodide pump activity (more iodide pumped in so more hormones produced), Increased iodination of tyrosine, Increased size/secretory activity of thyroid cells, Increased number of thyroid cells

TSH from the hypothalamus leads to:

T3

Only makes up 7% of thyroid hormone secretion, but is much more potent

Thyroxin (T4- most abundant), Triidothyronine (T3) and Calcitonin

3 Hormones secreted by the Thyroid Gland

Fat Metabolism

Metabolism that is enhanced by thyroid hormones

MIT and DIT

Molecules attached to the Thyroglobulin that both have iodine in them, which can replenish the cell itself with iodine when they break away from the protein

Concentration of TSH

Most important factor that influences the rate of iodide trapping by the thyroid

Coupling Reaction

Step in synthesis where the mono or diiodotyrosine residues get conjugated

Rate and Intensity of action

T3 & T4 have the same functions, but differ in their:

Shorter

T3's latency period is _____ than T4's

Colloid of the Glandular Follicles

The thyroglobulin that results from the synthesis, containing various amounts of T3 and T4, is stored for months in the ________

Na+/I- Cotransport System

The transport of iodide into follicular cells is dependent upon:

Hypothyroidism

This condition can also cause retardation because it slows physical and mental growth

Cellular Metabolic Activity

Thyroid hormone can increase this by increasing the number and activity of mitochondria

Increase

Thyroid hormones ______ blood flow to the tissues, cardiac output and heart rate

GI Tract

Thyroid hormones affect the ______ by increasing appetite as well as gastric secretions and motility

Lipid-soluble

Thyroid hormones are _____, so they cannot diffuse into plasma without a carrier protein

Transcription

Thyroid hormones can cause _____ of a large number of genes, resulting in an increased expression of numerous genes that govern metabolism

Decreased

Thyroid hormones cause _____ plasma levels of cholesterol, phospholipids, and triglycerides with increased levels of Fatty Acids

CNS

Thyroid hormones increase the rapidity of thinking (cerebration) in the ____

Metabolism

Thyroid hormones regulate _____

Carb Metabolism

Thyroid hormones stimulate almost all aspects of ________ by enhancing glycolysis, glucogenesis, and rate of glucose uptake

Iodizes table salt

To help prevent iodine deficiency (you need 50mg of ingested iodine per year), the food industry does what?

Muscle Weakness

Too much Thyroid Hormone results in _______ due to protein catabolism

Hypothalamus senses it and produces TRH, which transports through the median eminence to the Anterior Pituitary and stimulates Thyrotropin cells to produce TSH. TSH circulates until it reaches thyroid gland, where it promotes synthesis and release of T3 and T4. This elevation of T3 and T4 restores homeostasis

What happens when homeostasis is disturbed, causing a decreased level of T3 and T4 concentration?

Growth, CNS development, Cardiovascular Effects, and Metabolism

When T3/T4 diffuses into the cell and causes transcription and translation, it effects many other systems including:

T4

____ is diodinated into T3 in the peripheral tissues, which makes up most of the circulating T3

Respiration

______ is increased because thyroid hormones cause increased metabolism, which results in increased O2 demand and CO2 formation