Thyroid Flashcards
Symptoms of hypothyroidism
(Moms so tired) Memory loss Obesity Menorrhagia Slowness Skin and hair dry Onset is gradual Tiredness Intolerance to cold Raised BP Energy levels are low Depressed
Signs of hypothyroidism
(bRADYCARDIC) Reflexes relax slowly Ataxia Dry thin hair/skin Yawning Cold hands Ascites/non putting oedema Round puffy face Defeated demeanour Immobile C-CCF
Investigations of hypothyroidism
TFTs - free T4, TSH 1. Diagnose low T3,T4 2. Where is the problem? 1o - low T4, and High TSH 2o - low T4, and no compensatory increase in TSH
Treatment for hypothyroidism
Healthy and the young - levothyroixine(T4) 75-100mcg per day
Elderly and ischaemic heart disease - 25ug/day
How long does treatment for hypothyroidism take?
Clinical improvement within two weeks
Adjust dose every 4-6 weeks, T4 increases quickly TSH will take around six weeks
Pathogenesis of hashimotos thyroiditis
Autoimmune disease characterised by progressive destruction of the thyroid parenchyma “hurthle cell change” and mononuclear infiltrates without or with extensive fibrosis. It is mediated by multiple auto antibodies against thyroidperoxidase and TSH receptor
Clinical progression of hashimotos
Initial destruction of the thyroid gland can release the thyroglobulin colloid causing temporary hyperthyroidism(hashitoxocis) then euthyroid then hypothyroid
Painless enlargement of the thyroid
Amiodarone induced hypothyroidism
Used to treat heart conditions, this drug has a high iodine content. Inhibits the synthesis and release of the thyroid hormone and also conversion of t4 and t3
Other drugs that can cause hypothyroidism
Anti-thyroid medication, interferon-alpha and interleukin 2( malignancy), lithium (bipolar disorder)
Causes of hypothyroidism?
Autoimmune (hashimotos thyroiditis)
Primary(thyroidectomy, post radioactive iodine ablation, congenital biosynthesis defect, rare developmental abnormalities-thyroid dys genesis)
Secondary (pituitary, hypothalamic)
Antibodies in hypothyroidism
Anti-Tpo
Anti-Tg
Definition of hyperthyroidism
Over activity of the thyroid gland leading to excess thyroid hormone
Causes of hyperthyroidism
Graves disease Toxic multinodular goitre Toxic adenoma Ectopic thyroid tissue Exogenous
Symptoms of hyperthyroidism (sweating)
Sweating Weight loss Emotional lability Appetite increased Tremor/tachycardia due to af Intolerance to heat Nervousness Goitre and Gi upset(diarrhoea)
Signs of hyperthyroidism
Pulse is fast
Warm moist skin
Fine tremor
Lid lag(staring appearance)
TFTs for hyperthyroidism
- Diagnose high t3,t4
- Where is the problem ?
Decreased TSH suggests thyroid
Increased TSH suggests in or above pituitary
Other investigations for hyperthyroidism ?
Auto-antibodies for graves
ECG for AF
Radio-isotope scanning for “hot spots” –> toxic adenoma
Autoantibodies for graves disease
Thyrotropin receptor antibodies (TRABS)
Treatment for hyperthyroidism
B-blockers - rapid control of symptoms e.g anxiety and palpitations
Anti-thyroid medication
Partial thyroidectomy - thyroid gland is removed surgically leave some tissue plus parathyroid glands
Radioactive iodine - 131I is only absorbed by thyroid tissue, killing the cells and reducing thyroid hormone synthesis
Method of drug treatment in hyperthyroidism
- Block and replace - give carbimazole and thyroxine simultaneously less risk of iatrogenic hypo
- Titration - give carbimazole for 4 weeks reduce according to TFTs every 1-2 months
6months -31% remission
24 months -82%remission
Definition of graves disease
Autoimmune disease caused by circulating auto antibodies against TSH receptor so that thyroid hormones are produced in excess
Epidemiology of graves disease
Women 40-60years
Clinical features of graves disease
Thyrotoxicosis - classical signs of
Dysthyroid eye disease
Dermopathy - pretibial myxoedema (oedematous swelling above lateral malleolus)
Goitre- bruit as increased vasculature
Thyroid acropachy - clubbing, painful fingers
Graves Dysthyroid eye disease features
- exophthalmosis = bulging eyes
- upper lid retraction
- proptosis- eyes protruding from the orbit
- Diplopia- double vision
- nerve compression
- peri-orbital oedema
Definition of a goitre
A goitre is a swelling in the neck caused by an enlarged thyroid gland
Toxic goitre
Associated with hyperthyroidism
Non toxic goitre
Secrete normal or reduced levels of thyroid hormones
Two types of goitres
Diffuse - entire thyroid gland is enlarged caused by TSH induced hypertrophy and hyperplasia resulting in symmetrical enlargement of thyroid gland
Nodular- a thyroid nodule is a small lump in the neck
Types of nodule goitres
Multinodular- many lumps
Single nodule
-cyst- non cancerous like swelling
- adenoma- solid cancerous tumour
Diffuse non toxic goitre
Female : make = 7.1
Increased in pregnancy and adolescence
Often no thyroid dysfunction
Thyroid enlargement with inspiration strider and dysphasia
Management of diffuse non toxic goitre
Surgery - obstructive symptoms
Thyroxine suppression- if TSH>1, 58% of goitres smaller at 9 months
131- may reduce thyroid volume by 40% at one year
Features of benign nodules
FH hashimotos
FHA benign nodule/ goitre
Hypo/hyper symptoms
Sudden increase in size with pain
Features of malignant nodule
70 Male History of external neck radiation Recent changes in speech/ breathing/ swallowing Family history of thyroid cancer/ Men2
Clinical tools for recognising thyroid nodules
Palpable or impalpable
Consistency hard or soft
Motility fixed or mobile
Cervical lymph nodes
Investigations for thyroid nodules
Biochemistry FNAB- fine needle aspiration biopsy Scintigraphy- if TSH low, technetium 99m or 123 iodine, defines hot and cold areas, most malignant nodules cold Autoantibodies status Cxr Flow volume loop Thyroid ultrasound - suspicious features- solid hypoechoic, microcalcifications, absence of halo
Thyroid cancer two types
Differentiated (good prognosis) - papillary 17% - follicular 13-20% -mixed 50% Undifferentiated (poor prognosis) - anaplastic - small cell
Post op for thyroid cancer ?
Start t3 or t4 long term
Check calcium within 24 hr (fall predicts need for therapy add alpha calcidol if persists)
Maternal hypothyroid disease
T4 is important in Neurodevelopment T4 crosses the placenta but T3 doesn't Causes: - thyroid dysgenesis 85% (TSH receptor) -dyshormonogenesis Thyroid peroxidase, thyroglobulin, sodium iodide symporter
Jod basedow phenomenon
Hyperthyroidism following administration of iodine or iodide either as a supplement or contrast medium
Presents in patients with an endemic goitre(iodine deficiency) who move to iodine-abundant areas. Therefore does not occur in normal individuals
Wolf chaikoff effect
Hypothyroidism cause by ingestion or administration of large amounts of iodine
Used for treatment against hyperthyroidism to shut down hyper functioning gland or as an unpleasant effect of Amiodarone
Types of Amiodarone thyroid disease
Type 1 - Autoimmune Thyrotoxicosis tbx is high dose of carbimazole
Type 2 destructive thyroiditis tbx is glucocorticoids
Synthesis of thyroid hormone
- Accumulation of iodide ions
- absorbed as dietary inorganic iodine and absorbed through the na+ I- symporter on the basal membrane of they thyroid follicular cell
- pump is stimulated by TSH and inhibited by thiocyanate and nitrate - Oxidation of iodide
Iodide is oxidised to iodine by thyroid peroxidase - Iodisation of thyroglobulin
- the follicular cells are continuously synthesising glycoproteins called thyroglobulin
Rer-Golgi-vesicles- exocytosis into the lumen of the follicles
-Thyroglobulin is attached to tyrosine AAs
- Free iodine atoms are then incorporated into tyrosine residues
Binding of 1 atom to c3 = monoiodotyrosine (MIT)
Binding of 1 atom to c5 = diiodityrosine (DIT) - Coupling reactions
DIT + MIT. = alanine + thyroxine (t4)
DIT + MIT = alanine + 353 triiodothyronine (t3) - Modified thyroglobulin molecules are stored in colloid
