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