N212B Lecture 11 - Thyroid PDF

LECTURE 11: Thyroid and Parathyroid Disorders Basic Concepts ​ Endocrine glands: chemical messengers (hormones) into blood ​ Hypothalamus: sends signals to the pituitary gland ​ EPICENTER IS PITUITARY, “master gland”; controlling everything!! ​ Anterior pituitary: ○​ Rec...

LECTURE 11: Thyroid and Parathyroid Disorders Basic Concepts ​ Endocrine glands: chemical messengers (hormones) into blood ​ Hypothalamus: sends signals to the pituitary gland ​ EPICENTER IS PITUITARY, “master gland”; controlling everything!! ​ Anterior pituitary: ○​ Receives hormonal signals from hypothalamus ○​ Send out further signals ​ Posterior pituitary: ○​ Releases hormones synthesized by hypothalamus ​ End organs ○​ Adrenal cortex, thyroid, etc. KNOWWW THESE!!! ○​ Pituitary sends signals to these to produce more hormones ○​ Targets for pituitary hormones, may or may not secrete additional hormones Endocrine Disorders: Assessment and Diagnosis ​ ALWAYS ASK current and past medical history ○​ Know where they worked, if they’ve been in car accident recently ○​ Some disorders: wide-ranging, multi-system signs ○​ May affect mood and behavior ​ Immunoassays or blood levels of hormones ○​ Urinary hormone levels some instances ○​ Urine collection over 24 hrs ​ Suppression/stimulation tests ​ CT scan/MRI; ultrasound Endocrine Disorders: Treatments ​ Hormone replacement therapy ○​ Dosage schedules attempt to mimic physiological effects; correct something they’re low on so the body thinks there’s enough ⊙​ Pituitary works by neg feedback remember! ○​ Glucocorticoids, thyroid hormones, sex steroids, ADH most common replacements ​ Suppression of hormone overproduction ○​ Medications, surgery, radiation Thyroid ​ Triiodothyronine (T3) and thyroxine (T4) NEED TO REMEMBER THIS!! ○​ Iodine required for synthesis SUPER IMPORTANT TO REMEMBER ⊙​ Comes from diet ○​ Thyroxine ⊙​ Regulate body metabolism ​ Thyroid disorder more common in women ○​ Primary thyroid disorders most common; primary = organ has issues and that’s why there’s issues  ​ Enlarged thyroid ○​ Can indicate hypo- or hyperfunction ○​ Thyroid is on the neck, looks like butterfly, thicker on the sides, thin across Goiter ​ Enlargement of the thyroid ​ May or may not present with thyroid dysfunction signs and symptoms ○​ Sometimes it’ll have an effect, sometimes not when present ○​ Grows out usually, will have effect if pushing on something ​ May develop with: ○​ Excess TSH (thyroid-stimulating hormone) that comes from pituitary ○​ Low iodine levels ○​ Goitrogens ⊙​ Foods or other substances that promote thyroid gland enlargement Hypothyroidism ​ LOW thyroid levels (T3, T4) ​ Hashimoto’s thyroiditis ○​ Autoimmune disorder ○​ Anti-thyroglobulin and anti-thyroperoxidase antibodies ​ Other causes ○​ Drugs ○​ Genetics ○​ Thyroiditis (postpartum period especially high incidence) ○​ Congenital hypothyroidism: cretinism Hypothyroidism: Signs and Symptoms ​ COMMON TREND: slowing everything down!! ​ Cold intolerance ​ Weight gain (thyroxine is low, which helps metabolism) ​ Lethargy ​ Fatigue ​ Memory deficits ​ Poor attention span ​ Muscle cramps ​ Constipation ​ Decreased fertility ​ Puffy face ​ Hair loss ​ Brittle nails Hypothyroidism: Systemic Effects Factor Effect Reduced LDL receptors Hyperlipidemia  Elevated carotene Yellow-orange skin Decreased hematopoiesis Anemia Decreased renal function Increased susceptibility to drug toxicity; not filtering Myxedema Severe hypothyroidism; CRITICAL PATIENT Thyroid Disorders: Screening ​ American Thyroid Association ○​ Women at age 35 and every 5 years thereafter ​ American College of Physicians ○​ Women aged 50+ who have one or more clinical features of the disorder ​ Neonatal screening ○​ At birth, assess for elevated levels of TSH ○​ Identifies 90% of cases of congenital hypothyroidism Hypothyroidism: Diagnosis and Treatment ​ Diagnosis ○​ I FEEL LIKE THIS MAY BE TESTED ON ○​ Primary ⊙​ High TSH, low free T3, low free T4; T3 & T4 is resistant to pituitary, so we give replacement hormone ○​ Secondary ⊙​ Low TSH, low free T3 and T4; pituitary is talking to thyroid but NOT enough TSH to keep body going, cause is usually surgery!! ○​ Hashimoto’s thyroiditis ⊙​ Antithyroglobulin (anti-Tg) ⊙​ Antithyroperoxidase (anti-TPO) ○​ Ultrasound ○​ Blood laboratory values ○​ Screening tests ​ Treatment ○​ Replacement hormone ⊙​ Levothyroxine ○​ Surgical intervention ○​ Myxedema coma ⊙​ Severe hypothyroid condition ⊙​ Will progress to confusion and coma if untreated Hyperthyroidism ​ Elevated free T3 and free T4 ​ Graves’ disease ○​ Most common cause ○​ Thyroid-stimulating antibodies ○​ Autoimmune stimulation of the thyroid gland  ⊙​ Thyroid-stimulating antibodies bind to and activate thyroid tropin receptors within the thyroid gland, causing the gland to enlarge and to continually make thyroid hormones!!! SUPER EMPHASIZED ⊙​ Specific HLA tissue types ○​ Thyroid-stimulating immunoglobulins (TSIs) ⊙​ TSH receptor antibody (TRAb) ⊙​ Anti-TPO and anti-Tg antibodies ​ Other causes ○​ Subacute thyroiditis ○​ Postpartum period thyroiditis ○​ Thyroid adenoma; tumor ○​ Excessive TSH ○​ Toxic multinodular goiter ○​ Excessive iodine ingestion ⊙​ Jod-Basedow syndrome ○​ Secondary to pregnancy, HCG is similar to TSH; why it’s risk at postpartum period, can trigger thyroid receptors Hyperthyroidism: Signs and Symptoms ​ TREND: BODY WILL BE FASTER ​ Nervousness ​ Insomnia ​ Sensitivity to heat ​ Weight loss ​ Enlarged thyroid gland ​ Atrial fibrillation ​ Increased HR ​ Increased sympathetic nervous system sensitivity Hyperthyroidism: Signs and Symptoms ​ Exophthalmos ○​ Wide-eyed stare ○​ Extraocular area filled with mucopolysaccharides ​ Graves ophthalmopathy ○​ Periorbital edema and bulging of the eyes Hyperthyroidism: Diagnosis and Treatment Diagnosis Treatment Graves’ disease Antithyroidism hormone medication Serum thyrotropin receptor antibodies (TRAbs) Propylthiouracil (PTU), Carbimazole Radioactive iodine uptake (RAIU) test Radioactive I-131 ablation Hot, warm, and cold nodules Ultrasound with color Doppler evaluation Surgical intervention Blood: TRH, TSH, T3, T4 levels Note: biotin supplements can interfere with thyroid test accuracy!!! Hypothyroidism vs Hyperthyroidism!!! Myxedema coma = too low Thyrotoxic crisis (thyroid storm) = too high Thyrotoxic Crisis (Thyroid Storm) ​ Overwhelming release of thyroid hormones ○​ Serum-free T4 total T3: highly elevated ○​ TSH level: usually undetectable ​ Stimulate metabolism ○​ High fever, tachycardia, agitation, psychosis ​ Often precipitated by surgery or trauma ​ Medical emergency ​ Management ○​ Decrease thyroid hormone synthesis/production!! ⊙​ Methimazole or PTU ○​ Inhibit thyroid hormone secretion ⊙​ Oral potassium iodide or intravenous sodium iodide ○​ Reduce the heart rate ⊙​ Beta blocker and/or a calcium-channel blocker  ○​ Support the circulation with stress doses of intravenous glucocorticoids Thyroid Nodules ​ Most asymptomatic ​ Hypothyroidism or hyperthyroidism ○​ Single nodule: increased malignancy risk!!!! ○​ Multiple nodules: often benign ​ Ultrasound and needle biopsy for diagnosis ​ Technetium scan ○​ Uses radioactive isotope ○​ Hot, warm, cold nodule ⊙​ Hot = working a log, hyperactive ⊙​ Cold = hypoactive ⊙​ Warm = just right Malignant Thyroid Nodule ​ Age younger than 20 years or older than 70 years ​ Male sex ​ History of neck irradiation ​ Firm, hard, or immobile nodule; norm shouldn’t feel thyroid or lumps ​ Presence of cervical lymphadenopathy Parathyroid Gland ​ Four pea-sized glands on posterior thyroid (inside) ​ Secrete PTH (parathyroid hormone); REMEMBER PARATHYROID IS CONNECTED TO CALCIUM ○​ Released: ⊙​ Blood calcium low ○​ Activates: ⊙​ Bone resorption ⊙​ Intestinal calcium absorption by kidneys Hypoparathyroidism and Hyperparathyroidism Hypoparathyroidism Hyperparathyroidism Rare Parathyroid adenoma; TUMOR Inadvertent damage; thyroid surgery Primary: elevated PTH and calcium Signs/symptoms of hypocalcemia Secondary: response to hypocalcemia Chronic form: higher than normal BMD but still may Diagnosis: blood tests for PTH and serum calcium develop fractures Treatment: replacement PTH Treatment: parathyroidectomy for primary form, get Recombinant human PTH 1-84 out tumor Teriparatide (PTH 1-34)  Treatment: address hypocalcemia Treatment: reduce elevated serum calcium Calcium and vitamin D supplementation ALERT! ​ Myxedema coma ○​ May develop if hypothyroidism untreated ​ Thyrotoxic crisis ○​ Medical emergency ○​ Heart failure and pulmonary edema, ASSESS FOR TACHYCARDIA —- HEART WILL GIVE UP FOR TOO LONG, CIRCULATION IS POOR, not contracting efficiently, not relaxing to fill up enough, PULM EDEMA is because fluid backing up, not getting around to the entire body In which of the following ways does the thyroid use iodine? a.​ To stimulate the production of TSH b.​ To produce the thyroid hormones c.​ To regulate parathyroid production d.​ To destroy part of the thyroid gland Thyroid replacement therapy is indicated for the treatment of: a.​ Obesity b.​ Myxedema c.​ Graves (HYPERthyroidism) d.​ Cushing’s (HYPERcortisolism)