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Phys3 thyr & Parathy
Phys3 Thyroid & Parathyroids
| Question | Answer |
|---|---|
| 2 main cell types of thyroid? what do they produce? | 1.Follicle cells: produce T3 & T4 which is stored in the colloid. 2.Parafollicular cells (C-cells) produce calcetonin. |
| What all is contained within the Colloid of the thyroid follicles? | 1.Thyroid hormone (T3 & T4). 2.Thyroglobulin. |
| Synthesis of T3 | 1.Tyrosine residues of thyroglobulin are Ionated: once (MIT), twice (DIT). 2.Thyroperoxidase (TPO) adds MIT + DIT. |
| Synthesis of T4 | 1.Tyrosine residues of thyroglobulin are Ionatedonce (MIT), twice (DIT). 2.Thyroperoxidase (TPO) adds DIT + DIT. |
| Which is the more active Thyroid hormone? | T3. **T4 must be converted to T3 to become active |
| Which is synthesized/secreted more | T4 |
| How does TSH affect synthesis of thyroid hormone? | BINDS TO GPCR receptors 1.Inc production of Tg (thyroglobulin). 2.Inc production of TPO. 3.Activates Na/Iodine symporter via cAMP (brings Iodine into cell). |
| 3 types of deiodinases involved in thyroid hormone metabolism? where are they found? | 1.Type 1: catalyzes T4 to T3 (found in liver, kidney, thyroid). 2.Type 2: catalyzes T4 to T3 (found in brain, BAT, pituitary, cardiac & skeletal muscle, placenta, pineal). 3.Type 3: catalyzes T3 to T2 (found in brain, skin, placenta). |
| Receptor location for Thyroid hormones | INTRAcellular Alpha & Beta nuclear receptors despite the fact that its a PEPTIDE hormone. **T4 must be converted to T3 before it can bind to receptor. |
| Effects of Thyroid hormones | Normal Growth & metabolism: 1.Basal metabolic rate. 2.Carbohydrate metabolism. 3.Protein metabolism. 4.Lipid metabolism. 5.thermogenesis. |
| T3 stimulates gene expression of | 1.FA synthase. 2.GH. 3.Malic enzyme. 4.Glucose-6-phosphatase. 5.UCP. |
| How does cold influence release of TRH & TSH? | Increases their release from hypothalamus & pituitary. |
| Grave's Disease | Hyperthyroidism caused by autoimmune TSH receptor antibodies that stimulate/activate TSH receptor & Thyroid. |
| Symptoms of HYPERthyroidism | 1.Irritability & Anxiety. 2.Wgt loss & Inc appetite (Inc MET). 3.Inc B1 receptors & palpitations. 4.Diarrhea & Inc freq. 5.Heat intolerance. 6.Sweating & eye tearing |
| Hashimoto's Disease | Hypothyroidism caused by autoimmune thyroid cell antibodies that destroy follicular thyroid cells. |
| Symptoms of HYPOthyroidism | 1.Memory loss & depression. 2.Cold intolerance. 3.Dec appetite & Wgt gain. 4.Periorbital & peripheral edema. 5.Dry skin. 6.Constipation. 7.Chest pain & Dec CO. |
| Causes of Thyroiditis | Lithium drugs |
| Calcitonin | 1.Peptide hormone. 2.Produced by parafollicular (C-cells). 3.Affects tissues via GPCR. |
| PTH | PolyPeptide synthesized as a preprohormone in cheif cells & then cleaved into PTH |
| Regulation of Calcitonin secretion | 1.C cell [Ca]. 2.Ca receptors. 3.glucocorticoids. 4.glucagon. 5.GI hormones. |
| Regulation of PTH secretion | 1.Absolute [Ca]. 2.Rate of fall of [Ca]: A)Ca binding to cheif cell receptors. B)binding of Ca to its receptor. C)dec in [Ca] |
| 3 major effects of Decreased [Ca] on PTH? | 1.Less binding to Ca receptor stops the inhibition on exocytosis of PTH. 2.Inc synthesis of PTH. 3.Proliferation of Parathyroid cells. |
| Primary targets of PTH | 1.Bone. 2.Kidney. **Secondarily targets the GI via Vit D activation. |
| Effects of PTH on Kidney | BINDS TO GPCR receptor: 1.Stimulates Ca+ reabsorption. 2.Inhibits Phosphate reabsorption. 3.Stimulates 1-hydroxylase (activates Vit D). 4.Inhibits HCO3- reabsorption. |
| Effects of activated Vit D (due to PTH) on GI enterocytes | 1.Inc Ca+ absorption. 2.Inc Phosphate absorption. |
| 4 Major roles of activated Vit D | 1.Inc Ca+ absorption in small Intestine. 2.Inc Phosphate absorption in small intestine. 3.Inc Ca+ reabsorption in kidney. 4.Inhibits synthesis of PTH |
| Effects of PTH on Bone | Primary Effect: OSTEOLYSIS. this is accomplished by activating GPCR receptors on osteoblasts which then Increase OSTEOCLAST maturation & thus activity. |
| 3 ways PTH activated Osteoblasts Increase osteoclast maturation & activity | 1.Secrete M-CSF to activate osteoclast precursor maturation. 2.Juctacrine singaling via RANK ligand binding to receptors on osteoclast precursors leading to maturation. 3.Inhibits OPG which normally inhibits osteoclasts maturation. |
Created by:
WeeG
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