Nuclear Medicine Endocrinology Questions and Answers

Nuclear Medicine Endocrinology Questions and Answers Radionuclide type and doses used for thyroid imaging Tech 5-10 mCi injected - imaged 20 min later with pinhole I- uCi pill (IF uptake only: 100 uCi)- Images 6 and 24 hrs later with pinhole. 20% window at 159keV. I-131 3-4 mCi (IF uptake only: 10 uCi) 20% window at 364keV What is needed for uptake prior to administering I-123 / 131 and after pt. returns Prior administration: Count and record dose with probe at 20 cm neck phantom. After administration: count background At 6 hr: count and record with probe at pt's neck and back ground at pt's leg Previous Play Next Rewind 10 seconds Move forward 10 seconds Unmute 0:00 / 0:15 Full screen Brainpower Read More How to calculate uptake % and what is normal (pt thyroid cnts - pt bkg cnts) / (Standard cts - room bkg) x 100 Normal at 6 hrs: 6 to 18 % Normal at 24 hrs: 10 to 30 % Primary Causes of Hypotyroidism (diseases) Iodine deficiency (most common) goiter is common due to high circulating TSH constantly stimulating the gland Hashimoto (Autoimmune chronic, most common in USA) goiter is the mail clinical feature Over treatment with I-131 or meds Surgical removed Hashimoto thyroiditis is also called chronic lymphocytic thyroiditis autoimmune thyroiditis Grave's Disease a hyperthyroid autoimmune disease where the thyroid produces w/o the stimulation of TSH Right Thyroid Nodule Toxic Thyroid Nodule Toxic Multinodular Goiter I-123 and I-131 Radiopharmaceuticals used for Thyroid imaging I-123 Radiopharmaceutical for thyroid which has photon energy excellent for imaging I-131 Radiopharmaceutical for thyroid which has photon energy excellent for treatment Grave's disease Homogeneous, diffusely increased uptake of iodine by thyroid Toxic nodule/Multinodular goiter Heterogeneous uptake of iodine by thyroid with hot nodules Thyroiditis Depressed uptake of iodine by thyroid Hormones are _______________ or ______________ proteins or lipids what do horomones do increase or decrease the rate of cellular activity Which are the endocrine glands hypothalamus, pituitary (master gland), thyroid, adrenals, ovaries and testes hormones released by the hypothalamus are ______ (8) TRH, GnRH, PIH, GHRH/IH, CRH, MSH/IH Hormone of Major concern to us Thyrotropin Releasing Hormone what do the hormones released by the hypothalamus do and what kind of hormones are these they are petites and control the released of the anterior pituitary another name for anterior pituitary adenohypophysis how many hormones are secreted by the anterior pituitary, what type are they and which one is the main one 7 polypeptide - TSH (thyroid stimulating hormone) What does TSH trigger? it triggers the thyroid gland to uptake Iodine for the production of T3 and T4 (thyroxine) method for Iodine uptake active trasnport TSH causes what on the secretory cells of the thyroid mitosis, increasing size and weight of the gland how is TSH regulated ? by negative feed back. TSH is inhibited by the circulating levels T4 Hyperthyroid _________________ TSH Hypo _____________ TSH low high What is the screening test performed to eval the thyroid Normal levels: measuring TSH. Normal: 0.5-5.0 mU/L Can both TSH and T4 be low? why yes, if the cause is secondary hypothyroid due to hypothalamic or pituitary disease how much iodine is necessary to produce allergies and how much do we use one gram is necessary, we only use micrograms what are the 4 steps of thyroid hormone synthesis 1. iodide trapping 2. organification 3. coupling of MIT and DIT 4. proteolysis what is iodine trapping the active transport of Iodide into thyroid by follicular cells what is organification the attachment of both, iodide and the amino acid tyrosine making nonoiodotyrosine (MIT)and diiodotyrosine (DIT) what is coupling MIT +DIT = T3 DIT + DIT = T4 Thyroxine what is proteolysis the secretion of T3 and T4 into blood how is MIT and DIT stored ? by the thyroglobulin protein as a colloid in the follicular lumen what is the difference between Iodine and Iodide Iodine = I plus I = I2 (the element in the periodic table) Iodine = I- plus a metal+ = KI ( safe form for I ingestion) T3 and T4 are lipid soluble hormones T or F T which cells concentrate iodine? follicular parafollicular cells are involved with what calcitonine production Difference between T3 and T4 T3 (10%) 10 times more potent T4 (90%) what are sulfonylureas, methimazole and propylthiouracil ? how do they work antithyroid drugs they inhibit the organification and proteolysis Other treatments for hyperthyriodsm are? ablation and radionuclide therapy Do antithyroid drugs prevent Iodine trapping? No How many parathyroid glands are there 4 or more What does the parathyroid hormone do? regulates Ca levels in blood by increasing osteoclast increasing Ca reabsorption in kidney increasing Vit D3 production for the absorption of Ca and Mg from the GI tract what are the 2 types of disease of the thyroid? function and structure The 2 disorders of function are Hyper and Hypothyroid Disorders of structure do not cause hyper or hypo, they are multinodular goiter adenomas carcinoma a proper eval of the thyroid gland includes what? clinical exam labs nuc med scans and uptakes Hyper and hypo thyroid always refer to the amount of what hormone/s? T3 T4 An uptake test does not diagnose hyper from hypo T or F T An uptake test differentiates Graves from subacute thyroiditis graves vs subacute thyroiditis graves: autoimmune disorder hyperthyriod SAT: viral infection hyperthyroid what are normal upatake levels at 6 and at 24 hrs At 6 hours: 3% to 16% At 24 hours: 8% to 25% Disorder of function hyperthyroidism is a type of thyrotoxicosis nucmed helps diferenciate thyrotoxicosis cause by ... and thyrotoxicosis cause by... hyperthyroidism, not hyperthyroidism (graves, overproduction outside gland, leakage from gland) clinical symptoms of hyper vs hypo hyper: weight loss, heat intolerance, diarrhea, exophthalmos, tachycardia, constant hunger hypo: weight gain, cold intolerance, constipation, slow heart rate mental lethargy, Both: fatigue, skin issues, hair thinning, what are the causes of hyperthyroidism ? (diseases) Graves' (autoimmune disease, most common ) Plummer's (solitary nodule of unknown origin) Multinodular goiter Thyroiditis (viral/bacterial infection) Iodine induced thyrotoxicosis (excess contrast) Rare: (may be etopic) thyroid cancers teratomas (in ovaries or testes) struma ovarii How does Graves' show on scans? 4 facts diffusely increased 1. an autoimmune disease cause exophthalmos 3. 5 x more common in women 4. common between ages of 20-40 how does Plummer show on scans 3 facts focal hot spot 1. solitary nodule (adenoma) 2. has autonomous fuction of hormone production 3. also called toxic nodular goiter how does mutinodular goiter show on scans facts coarsely patchy cold regions 1. less chances of being cancer than solitary cold nodules 2 types of hypothyroidism Primary: thyroid failure to produce and release hormone Secondary: thyroid works but TSH is deficient (congenital cretinism or pituitary tumor)