Copy of 17+%26+18-Thyroid+Disorders

8/3/2019 Copy of 17+%26+18-Thyroid+Disorders

1/66

Thyroid Disorders


2/66

Anatomy

Over Trachea

Two Lobes

connected

together by anisthmus

15 to 20 g


3/66

Thyroid gland

Thyroid gland derives from the floor ofembryonic pharynx

Begins to develop around 4 weeks of gestation

Moves downthe neck while forming its

characteristic bilobular structure Thyroid development is largely completed

between 10-20 weeks of gestation

Thyroid gland size increase gradually by

1g/year until age of 15 years were itachieves

adult size (15-25 g)


4/66

Sites ofnormal & ectopicthyroid tissue


5/66

Thyroid gland

Thyroid gland is composed overa millioncluster of follicles

Follicles are spherical & consists of

epithelial cells surrounding acentralmass (colloid)

Thyroglobulin is storage room

Two main hormones:

Tetraiodothyronine (Thyroxin)

Triiodothyronine


6/66

FUNCTIONAL

UNIT IS

THEFOLLICLE


7/66

Thyroid gland

Thyroid gland normally secretes mainly T4 70 % of T3 derived from T4 in peripheral

tissues

T4 is converted to T3 by 5-deiodinase enzyme

Both T4 and T3 are in bound form (TBG, prealbuminand albumin)

Only 0.025% of T4 and 0.35% of T3 are free

Free hormone concentration bestcorrelates

with thyroid status

T4 production is 5-6 Qg/kg/day in infancy withgradual decrementto 1.5 Qg/kg/day inadult


8/66

Thyroid Regulation

Somatostatin,Glucocorticoid

Dopamine


9/66

Thyroid hormone synthesis

1) Iodide pump Rate limiting step inthyroid hormone synthesis which

needs energy

Follicles have intheir basement membrane an iodidetrapping mechanism which pumps dietary I - into the cell

Normal thyroid: serum iodine is 30-40:1 Iodide uptake enhancers:

TSH

Iodine deficiency

TSH receptors antibody

Iodide uptake inhibitors

Iodide ion

Drugs

Digoxin

Thiocynate

per chlorate


10/66


2) Iodide oxidationto iodine and Organification

Inside the cells, iodide is oxidized by

peroxidase system to more reactive iodine

Iodine immediately reacts with tyrosineresidue onathyroid glycoproteincalled

thyroglobulinto form : T1= mono-iodotyrosyl thyroglobulin

T2= di-iodotyrosyl thyroglobulin

Both processes are catalyzed by thyroid

peroxidase enzyme


11/66


3) Coupling

T1& T2 couple togetherto form T3&T4

MIT +DIT = T3 (Tri-iodothyronine) DIT + DIT = T4 (Thyroxin)

All attached to thyroglobulinand stored inthecolloid Thyroglobulin molecule

This process is stimulated by TSH


12/66

Production of Thyroid Hormones

NIS (Na+/I- Sympoter)

TPO


13/66

Effects ofthyroid hormones

Fetal brain & skeletal maturation Increase in basal metabolic rate

Inotropic & chronotropic effects on heart

Increases sensitivity to catecholamines Stimulates gut motility

Increase bone turnover

Increase in serum glucose, decrease in

serum cholesterol

Conversion ofcarotene to vitaminA

Play role inthermal regulation


14/66

Increase BMR ( Basal Metabolic Rate )

cellular metabolicactivity by :

size, total membrane surface & number of

mitochondria

ATP formation

active transport of ions ( Na+, K+ )

Promote growth & development ofthe brain during

fetal life and forthe first few years of postnatal life


15/66

Carbohydrate metabolism

enhanced glycolysis, gluconeogenesis,

GI absorption & insulin secretion

Fat metabolism

enhanced fat metabolism

Accelerates the oxidation of free fatty acids by the cells

plasmacholesterol, phospholipids & triglycerides

Body weight

the appetite, food intake, GI motility but the body weight


16/66

Cardiovascular system

vasodilatation

blood flow

cardiac output

heart rate

Respiratory

the rate and depth respiration

CNS

extreme nervous & psychoneurotic tendency

Muscle

make the muscles react with vigor ----->

muscle tremor ( 10-15 times/sec )

Sleep: extreme fatigue but is difficult to sleep


17/66

Causes , Clinical Features &

Consequences of Hypothyroidism

Congenital Hypothyroidism

Acquired Hypothyroidism


18/66


19/66

Etiology

Congenital

Acquired

Primary

Secondary

Tertiary


20/66


Occurs inabout 1/4000 live birth Thyroxin is important for CNS developmentand

postnatal growth

The most frequentcause is congenital absence

ofthe thyroid gland (athyrosis) Presentations may include cyanosis, prolonged

hyperbilirubinemia, poor feeding, hoarse cry,

umbilical hernia, respiratory distress,

macroglossia, large fontanelle, and delayedskeletal maturation

Rarely, neonatal hypothyroidism is transient


21/66


Etiology

1) Thyroid dysgenesisIdiopathic:

Commonestcause in 95% ofcases Athyreosis (40%)

Hypoplasia (40%)

Ectopia (base oftongue, midline) (20%)

2) Thyroid dyshormonogenesis (A.R) (10%)

3) Hypothalamic-pituitary hypothyroidism Anencephaly, holoprosencephaly, S.O.D

idiopathic


22/66


23/66


4) Transient hypothyroidism Maternal TRAB

Maternal ingestion of goitrogen

5) Drugs

6) Iodine excess

7) Iodine deficiency


24/66

Anti-thyroid Drugs and fetus

Thionamides

PTU & MZT

Iodide

Lithium

Amiodarone

Radioiodine

After 10-12 wk gestationcan damage

fetal thyroid gland


25/66

Presentations ofcongenital hypothyroidism

Macroglosia Prolonged hyperbilirubinemia

Poor feeding

Hoarse cry

Decreased activity Constipation

Umbilical hernia

Dry yellow skin large fontanelle

Delayed skeletal maturation


26/66

Neonatal screening forcongenital hypothyroidism

Routine in mostcountries worldwide

Filter paper blood spot measuring TSH

Why ??

Clinical manifestations at birth, usually are subtle or

evenabsent (passive transplacental maternal thyroxin)

At birth, surge of TSH (stress of delivery) up to 30 -40

u/ml

Early detection will prevent mental retardation or

decreasing IQ ofaffected neonates

Thyroxin is important for CNS development from birth till

3 years of life

Screening program will miss 2ry/ tertiary cases

The program is hampered by a high rate of false

positive results


27/66


More commonthan hyperthyroidism 99% is primary (< 1% due to TSH deficiency)

Hashimotos

mostcommonthyroid problem (4% ofpopulation)

mostcommoncause in iodine-replete areas

chronic lymphocyticthyroiditis

Associated with TPO antibodies (90%), lesscommonly Tg antibodies

Iatrogenic Hypothyroidism from radioactiveiodine therapy


28/66


Subacute thyroiditis

Painful, often radiates to the ear

c/o malaise, pharyngitis, fatigue, fever, neck pain/swelling

Vir al etiology (URI/ pharyngitis)

self-limited. Cantx inflammation w/ ASA, NSAIDs or steroids Suppurative/ Acute Infectious thyroiditis

Infections ofthe thyroid are rare

normally protected from infection by its thick capsule

Bacterial >> fungal, mycobacterial or parasitic

Pts are acutely ill w/ a painful thyroid gland

assoc w/ fever/chills, anteriorneck pain/swelling, dysphagia

and dysphonia


29/66


Symptoms General Slowing Down

Lethargy/somnolence

Depression

Modest Weight Gain

Cold Intolerance

Hoarseness

Dry skin

Constipation ( peristalticactivity)

GeneralAches/Pains Arthralgias or myalgias

(worsened by cold temps)

Brittle Hair

Menstrual irregularities Excessive bleeding

Failure of ovulation

Libido


30/66


Examination Dry, pale, course skin with yellowish tinge Periorbital edema

Puffy f ace and extremities

Sinus Bradycardia

Diastolic HTN Body temperature

Delayed relaxation of reflexes

Megacolon ( peristalticactivity)

Pericardial/ pleural effusions

Congestive heart failure Non-pitting edema

Hoarse voice

Myopathy


31/66

Goiter

A swollenthyroidgland

Assessment;

how big, how quickly

has it developed, isit smooth ornodular,

is it painful, any

associated lymph

nodes, any sudden

changes, is it bigenough to cause

local symptoms (e.g.

breathing problems)


32/66

Myxedema


33/66

Hypothyroidism --- loss of scalp hair

A ColorAtlas of Endocrinology p70


34/66

Hypothyroidism with short stature


35/66

DiagnosisCongenital hypothyroidism

Thyroid hormone level TSH

Thyroid scan


TSH fT4

Thyroid antibodies

Thyroid ultrasound

TSH: low in secondary hypothyroidismhigh in primary hypothyroidism

TRH test: to differentiate between secondary& Tertiary hypothyroidism


36/66

Euthyroid sick syndrome

Abnormalities inthyroid functiontestsobserved with systemicnonthyroidal illness

Cytokine mediated

Reduced TRH release, TSH response, T4

production/release, T4 to T3 conversionandTBG production

Increased somatostatin secretion

Inhibitory effects of dopamine and

glucocorticoid on TRH action

Very low T4 values have a poor prognosis


37/66

Treatment

L-thyroxin replacement should be startedas soonas possible

Iftreatment is delayed > 2 months of life,

> 75% risk of hypothyroidism Onthe other hand, delayed treatment of

hyperthyroidism will lead to advancedskeletal maturation, craniosynostosisand intellectual deficits

L-Thyroxin is the main drug fortreatmentof hypothyroidism, whatever is the cause


38/66

Treatment

8-10

6-8

5-6

4-5

2-3

25-50

50-75

75-100

100-150

150-200

0-6

6-12

1-5

6-12

>12

L-Thyroxin dose

Qg/ kg/day

L-Thyroxin dose

Total dose (Qg/day)

Age


39/66

Causes , Clinical Features &Consequences of Hyperthyroidism


40/66

Hyperthyroidism (Thyrotoxicosis)

Definition Excessive secretion of T3 & T4

Affects metabolic processes inall body

organs Hyperthyroidism is 4-10 times more

prevalent in women

Mostcommon endocrine disease secondonly to diabetes as the most occurring

endocrine disease


41/66

Thyrotoxicosis

Causes

Transient

1.Neonatal thyrotoxicosis

2.Infectious : Acute & subacute thyroiditis3.Drug induced: Amiodarone, interferon &interleukin

4.Iatrogenic


42/66

Thyrotoxicosis

Causes

Persistent

1.Graves disease

2.Toxic multinodular goiter

3.Toxic solitary adenoma

4.Central (pituitary origin)


43/66

Neonatal Thyrotoxicosis

Only occur with 5% ofthyrotoxic mothers

Severity consistent in future pregnancies

20% mortality if untreated

Evolves rapidly, evident by day 7 of life, unlessTRAB blocking antibody is present

Associate with cranial synostosis and learningdifficulties, ifnottreated

Fetal thyrotoxicosis in rats leads to abnormalCNS myelination

Parents should be aware of potential learningproblems (early school years should bemonitored)


44/66

Neonatal hyperthyroidism bornto mother

with Graves disease



45/66

Graves disease

Pathogenesis T-cell dependentautoimmune disease

60% have HLAassociation with A1, B8,DR3,DR4,DR5

Autoimmune disorderthat results inproduction ofantibodies directed againstthyroid antigens:

TS

H receptors Thyroglobulin

Thyroid peroxidase


46/66

Subacute Thyroiditis

Clinical course lasts weeks to months Acute phase (2-6/52) with clinical and

biochemical hyperthyroidism

Recovery phase (weeks-months) transient

hypothyroidism then euthyroidism

Clinically, history of sore throat, fever, tender

goiter, cervical lymphadenopathy

High ES

R, negative antibodies and absentradioactive I131 uptake


47/66

Hyperthyroidism

May result in significant morbidity,

mortality & even death

Symptoms Jittery, shaky, nervous

Difficulty concentrating

Emotional lability Insomnia

Rapid HR, palpitations, Feeling Hot

Weight Loss

Diarrhea Fatigue

Menses : lighter flow, shorterduration


48/66

Hyperthyroidism

Exam Eye findings (20%)

Goiter

Thyroid brui t orthrill

Tachycardia: Sinus Tachycardia,

Atrial Fibrillation Flow murmur

Systolic hypertension

Hyperreflexia

Tremors

Proximal muscle weakness Clubbing

Onycholysis (


49/66

Thyrotoxicosis

Heart: Increased heart rate, contractility andcardiac output

Skeletal muscles: Proximal myopathy, easyfatigability and muscle atrophy

Gonads: Irregular menstrual cycles,impotence

Liver: Low cholesterol LDL & apolipoprotein

Bone: Increased bone turnover, osteoporosis& increased risk of fracture


50/66

Grave's ophthalmopathy

The pathogenesis of infiltrativeophthalmopathy is poorly understood

It may occur before the onset ofhyperthyroidism oras late as 15 to 20 years

The clinical course of ophthalmopathy is

independent ofthe clinical course ofhyperthyroidism

Infiltrative ophthalmopathy may result fromimmunoglobulins directed to specificantigensinthe extraocular muscles & orbital fibroblasts

The antibodies are distinct from those initiatingGraves'-type hyperthyroidism


51/66


52/66

Hyperthyroid Eye Disease

Hyper thyroidism (any cause)

Lid lag, lid retractionand stare

Due to increased adrenergictonestimulating the levator palpebralmuscles.

True Gr aves Ophthalmopathy Proptosis

Diplopia

Inflammatory changes

Conjunctival injection

Periorbital edema Chemosis

Due to thyroid autoAbs thatcross-react w/ Ags in fibroblasts, adipo-cytes, + myocytes behind the eyes.


53/66

Exophthalmos

G hth l th


54/66

Graves ophthalmopathy


55/66

Hyperthyroid Eye Disease


56/66

Graves Dermopathy

Thyroid Dermopathy

Thickening and redness of

the dermis

Due to lymphocytic

infiltration


57/66

Thyroid Acropachy

Thyroid acropachy. This is most marked in the index fingers and thumbs


58/66

Tremor ofthe hand



59/66


60/66

Diagnosis

TSH level usually < 0.05 Qu / ml 95 % ofcases, high FT4 & FT3

In 5% high FT3 with normal T4 (T3

Thyrotoxicosis) Thyroid receptor (TRAB) are usually

elevated at diagnosis

Antibodies againstthyroglobulin,peroxidase or both are present inthe

majority of patients


61/66


62/66

Thyrotoxicosis- Treatment

Three modalities for more than last 50 years

Radioactive iodine,antithyroid drugs&surgery

None is optimal

None interrupts the autoimmune process Each has a drawbacks

There is no treatment for underlying cause

No other research options so far


63/66

Neonatal Thyrotoxicosis

Treatment

1) Lugols iodine

1 drop tid for 1-2 / 7

Dramaticcoarse therapy

Blocks T4 release, synthesis and I uptake(Wolf Chaikoff effect)

2) Propranolol

3) Carbimazole

will take several days to have an effect on T4synthesis


64/66

Hyperthyroidism (Treatment)

1) -blockers (symptom control) Propr anolol (Inderal )

Atenolol (Tenormin)

Metoprolol (Lopressor)

2) 131-RAIA (70% thyroidologists prefer) Dosing

Graves: 10-15 mCi

Toxic MNG/Adenoma: 20-30 mCi

Absolute contraindications

Pregnancy and lactation (excreted in breast milk)!

Pregnancy should be deferred forat least 6 months followingtherapy with radio-active 131

It is advisable to avoid 131-Rdio-active iodine therapy in patientswith active moderate severe Graves ophthalmopathy.


65/66


3) Antithyroid Drugs (30% thyroidologists prefer) Propylthiouracil (PTU)

100 mg bid-tid to start

Methimazole

10X more potentthe PTU

10 mg bid-tid to start Complications ofATDs

Agranulocytosis (1/200-500)

usually presents w/ acute pharyngitis/ tonsilitis or pneumonia.

Rash

Hepaticnecrosis, Cholestaticjaundice Arthralgia


66/66


4) Surgery (sub-total thyroidectomy)

Indications

Patient preference

Large or symptomatic goiters

Whenthere is question of malignancy Need to be euthyroid priorto surgery

To the risk ofarrhythmias during induction ofanesthesia

To the risk ofthyroid storm post operatively

ATDs + -blockers

Risks Permanent hypoparathyroidism

Recurrent laryngeal nerve problems

Permanent hypothyroidism

Documents

Copy of 17+%26+18-Thyroid+Disorders