collated thyroid pbl

8/3/2019 Collated Thyroid Pbl

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HYPERTHYROIDISM: EPIDEMIOLOGY

Australia

-Around 1 in 20 people will experience some form of thyroid dysfunction in their lifetime.

-Around 2 in every 100 women will experience some degree of hyperthyroidism.

-Its likely that at any time there are approximately 850,000 Australians with thyroid disease of somekind, often going undiagnosed.

United States

-Graves disease is the most common form of hyperthyroidism (60-80% of thyrotoxicosis). The annual

incidence is 0.5 cases per 1000 persons during a 20-year period, with the peak occurrence in people

aged 20-40 years.

-Toxic multinodular goiter (15-20% of thyrotoxicosis) occurs more frequently in regions of iodine

deficiency. Most persons in the U.S. receive sufficient iodine, and the incidence of toxic multinodular

goiter is less than the incidence in areas of the world with iodine deficiency.

-Toxic adenoma is the cause of 3-5% of cases of thyrotoxicosis.

International

-The incidences of Graves disease and toxic multinodular goiter change with iodine intake.

-Compared with regions of the world with less iodine intake, the U.S. has more cases of Graves

disease and fewer cases of toxic multinodular goiters.

Race

Autoimmune thyroid disease occurs with the same frequency in Caucasians, Hispanics, and Asians,

and it occurs less frequently in the black population.

Sex

All thyroid diseases occur more frequently in women than in men. Graves autoimmune diseaseoccurs in a male-to-female ratio of 1:5-10. The male-to-female ratio for toxic multinodular goiter and

toxic adenomas is 1:2-4.

Age

-Autoimmune thyroid diseases have a peak incidence in people aged 20-40 years.

-Toxic multinodular goiters occur in patients who usually have a long history of nontoxic goiter and

who therefore typically present when they are older than 50 years.

-Patients with toxic adenomas present at a younger age.

Thyroid cancer

-Thyroid cancer is the most common endocrinological malignancy-More common in women than men.

-Incidence rates vary geographically, with the highest rates occurring in North America (8.1 per

100,000 females) and the lowest rates in Western Africa (1.4 per 100,000 females).Malta has the

highest incidence rate in the European Union, with 12.6 per 100,000 females affected, compared to

the rate in the UK of 3.1 per 100,000.

-In US, thyroid cancer accounts for 1% - 1.5% of all new cancer cases reported annually. It is

estimated that about 30,000 new cases of thyroid cancer are diagnosed annually in the US and about

1400 people die of the disease.The median age at diagnosis is 40-45 years.
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Iodine and Thyroid

Iodine:

Not created by the body needs to be part of diet Found in bread, iodised table salt, saltwater fish, seaweed, soy milk Over 80 years, worldwide efforts have been made to eliminate iodine-deficiency. Strategies

include:

o Iodized salto Iodine in bread (Australia and NZ)o Iodine injections in areas without wide-spread iodized salt accesso Iodination of water supplies

Essential for making thyroid hormone T4 and T3

Iodine deficiency can cause:

Goitreo Without adequate iodine, thyroid progressively enlarges to keep up with demand for

thyroid hormone production

o Most common cause of goitreo Can lead to hyperthyroidism

Hypothyroidismo Most common cause of hypothyroidismo As bodys iodine levels fall, hypothyroidism may develop since iodine is essential for

making thyroid hormone

Pregnancy-related problemso Iodine is important in pregnancy or during infancyo Even mild iodine deficiency has been associated with miscarriage, stillbirth, preterm

delivery and congenital abnormalities in their babies (mental retardation, problems

with growth, hearing and speech)

o In severe iodine deficiency a syndrome called cretinism can occur (permanentbrain damage, mental retardation, deaf mutism, spasticity and short stature); not

seen in Australia


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Iodine excess:

Can trigger autoimmune thyroid disease and hypothyroidism Theory:

o High iodine intake can initiate and worsen infiltration of the thyroid of lymphocytes(due to chronic irritation / injury).

o Large amounts of iodine blocks the thyroids ability to make hormonePeople from iodine-deficient regions who move to iodine-sufficient regions may also experience

problems since their thyroids have become very good at taking up and using small amounts of iodine

iodine-induced hyperthyroidism

Potential sources of excess iodine:

Medications (amiodarone) Radiology procedures (iodinated intravenous dye) Diet

Iodine controversy: too much vs not enough

Small risks of chronic iodine excess are outweighed by the substantial hazards of iodinedeficiency

Pathophysiology nikjaja


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Three main types of clinical thyroid disease:

1. Secretory malfunction: hyper- or hypothyroidism2. Swelling of the entire gland: goitre3. Solitary masses: one large nodule in a nodular goitre, adenoma or carcinoma


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Types of thyroid cancer (Sara)

Papillary & Follicular ca (well-differentiated thyroid ca)

Slow-growing tumour of follicular cells Histological psammoma bodies in 50% Propensity for local invasion & metastases Most common thyroid ca (~80%) (3x > common in women) Appear s after 10-20 year latency RF: (childhood) radiation exposure, Hashimoto thyroiditis

Medullary thyroid ca (MTC)

Tumour of parafollicular (C cells) Histological amyloid deposits in stroma (green bifringence on Congo red staining) Represents 5% of thyroid malignancy (75% sporadic, 25% familial) Mostly arise in middle & upper 1/3 of lobes (sporadic-unilat, familial- both) Elevated serum calcitonin levels are diagnostic Prognosis worse cf well-differentiated thyroid ca

Anaplastic thyroid ca

One of the least common (1.6%) Rapidly growing thyroid mass Histologically highly variable appearance focal areas of necrosis & haemorrhage Most aggressive biological behaviour + Worse survival rates for all malignancies in general Present in 6th-7th decade of life w symptoms of local invasion

Primary Thyroid Lymphoma

Represent 2-5% of thyroid malignancies Mostly non-Hodgkins B cell tumours 2nd most common = low grade malignant lymphoma of MALT Assoc. w Hashimotos thyroiditis

Sarcoma of thyroid gland

Uncommon, aggressive tumours arising in stromal or vascular tissue in gland Important to dy/dx this from anaplastic thyroid ca Unresponsive to chemo, recurrence common, prognosis poorReference

eMedicine


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Investigations Eric

Thyroid Function Tests

Test Comment Normal Value

TSH Test of choice 0.3-5.0 mIU/L

Total T4 Bound & Free T4 5.0-12.5 g/dL

Free T4 Functional (Free) T4 0.7-2.0 ng/dL

Total T3 Only in HYPER evaluation 80-180 ng/dL

Free T3 Rarely used 2.3-4.2 pg/mL

Thyroid Auto-Ab +ve in Hashimoto disease Titre < 1:100

TSI +ve in Graves disease < 1.3 (index)

Thyroglobulin Follow-up thyroid Cancer (Depends)

Principles:-Correlate w Hx, Ex (Sg, Sx of HYPER, HYPO)-Disease prevalence 0.6% (1:1 HYPER:HYPO)-Co-morbid Inaccurate? Rpt post-acute

-TSH first test Abn? Free Thyroxine (T4)

-Drugs (iodine contrast, esp inpatient) Abn?

Further Evaluation-HYPER RAIU +/- scan-Nodule FNA/FNB-HYPO Auto-Ab (+ve = Hashimoto)-Subclinical HYPO Rpt TFTs in 6m

-Sick Euthyroid Rpt TFTs post-acuteTFT Algorithm (Of Sorts!!)

TSH

[ ] FT4

[]

A-Ab

"-ve" Severe Illness / Drugs (Iodine) / Idiopathic

"+ve" Hashimoto Thyroiditis

[] Subclin HYPO / Insufficient T4 Rx

[ ] THS-oma / Peripheral Resistance

[] Further workup if CNS disease suspected

[ ]


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Mechanism Indications Contraindications Side Effects

/Complications

Drugs :

Thioureas/

Thionamides

Examples

carbimazole,

propylthiouracil

and

methimazole

Inhibits the iodination of

tyrosine on thyroglobulin,

which consequently

decreases T3/T4 synthesis

Also inhibits deiodination of

thyroxine (prevents it from

becoming triiodothyronine)

Orally active

- Decrease in thyroidhormones only

occurs after the

bodys stores have

been depleted

(weeks)

- The half life of T4 isabout 7 days

Does not effect exopthalmus

Prolonged use

(particularly for

Graves Disease)

Young patients (propylthiouracil

- Causes congenitalhypothyrdoism (baby

is born with goitre

and cretinism)

Agranulocytosis

Rashes (2-25%)

Headaches,

nausea, jaundice

and joint pain

Agranulocytosis

Iodine/Iodide Small amounts in the diet are

necessary for thyroid functionHigh doses inhibit release of

T3 and T4

Short term treatment

- Only inhibitshormones

for a few

days or

weeks

Thyrotoxic crisis

Preparation for

thyroidectomy

Allergic reactions

Radioiodine/

Radioactive

Orally active

- Taken up andaccumulated by

thyroid

- Incorporated intothyroglobulin

Emits -particles (localised

cytotoxic action)

Half life 8 days approx

Recurrent

Hyperthyroidism

Thyroid carcinoma

Older patients

Pregnancy

Childhood

Hypothyroidism

Thyroid Cancer

Symptomatic

Relief

(-adrenoceptorantagonists eg.

Does not affect thyroid

hormone levels

Reduces some of the signsand symptoms of

In short term while

waiting for

thionamides andiodine to take effect


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Propranolol,

metoprolol or

atenolol)

hyperthyroidism

- Tachycardia- Arrythmias- Angina- Tremor- Agitation

For hyperthyroid

crisis

Preparation for

thyroidectomy

HYPOTHYROIDISM Management Dilini

Aim of Treatment increase thyroid hormone or replace

hormone

Mechanism Indications Contraindications Side Effects

/Complications

Thyroxine (T4)

(Levothyroxine

oroxine)

Orally Active

Action

- Maximum effect in10 days

- Duration of action= 3 weeks

For all symptomatic patients

with hypothyroidism

Large doses are

contraindicated in the

elderly

- Due to riskfactors

-

Angina

Arrythmias

Heart Failure

Oesteoporosis??

Due to over-

replacement of

thyroid hormone

Triiodothyronine

(T3)

Hypothyroid crisis

- Eg. Myxoedemacoma

- Used via i.v

Complications Jess

Hyperthyroidism Thyrotoxic cardiomyopathy heart failure

o May also be related to high-output HF Angina AF

o seen in 25%, warfarinise unless contraindicated, mx: control hyperthyroidismo Most common in pts >40

Osteoporosiso Due to bone mineral losso Severity is related to time of untreated hyperthyroidism

Gynaecomastia Thyroid storm

o Treatment includes beta-blockers, antithyroid drugs, supportive care, and corticosteroids; an endocrinespecialist should be consulted


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Opthalmopathyo Retro-orbital inflam + lymphocyte infiltration swelling of the contents of the orbital contentso May occur if pt is hypo/hyper/euthyroid

Complications of hypothyroidism Angina

o High initial dose of levothyroxine Resistant hypothyroidism

o Generally due to non-compliance AF

o Over-tx Osteoporosis

o Over-tx Myxoedema coma

o Generally occurs an older pts w multiple co-morbidities and a long period of untreated illnesso Life-threatening condition where untreated, severe hypothyroidism rapidly deteriorateso Precipitated by another underlying illness

Adrenal crisiso Levothyroxine tx in the setting of adrenal insufficiencyo Treat initially w glucocorticosteroids

Tx-related thyrotoxicosiso Over-tx

Post-op complications (general) Pain Pyrexia

o Atelectasis (mx: physio, NOT abx)o Tissue damageo Necrosiso Infection

Do a thorough infection screen (pneumonia, wound, abdo [peritonism], UTI, IV lines,meningism, endocarditis)

o DVTo Choose Ix based on clinical findings

Confusiono Hypoxiao Drugs (opiates, sedatives, &c.)o Urinary retentiono MIo Strokeo Infectiono EtOH withdrawalo Liver/renal failure

Dyspnoea/hypoxiao Pneumonia/pulmonary collapse/aspirationo LVF (MI/fluid overload)o PEo Pneumothorax 2ary to CVP line or IC anaesthetic block)

BP dropo Compare to BP pre-opo Hypovolaemia (replace fluid losses w/ colloid)o Haemorrhage (check wound sites for evidence)o 2ary to MI, PEo Consider sepsis and anaphylaxis

Oliguriao Urinary retention (common) replace lost fluidso Renal failure following shock, nephrotoxic drugs, trauma, transfusiono If anuria: consider malsited cathether, obstruction, or two ureters tied during surgery

N/Vo Mechanical obstructiono Paralytic ileuso Medications

Haemorrhageo 1ary

Continuous bleeding, starting during surgery. Replace blood loss and if severe, return to theatrefor haemostasis

o Reactive Haemostasis appears secure until BP rises and bleeding starts. Replace blood and re-explore

woundso 2ary

Occurs 1-2 weeks post-op and is the result of infection Wound dehiscence Incisional hernia (abdominal surgery)


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Post-op complications (Thyroid surgery) Recurrent and/or superior laryngeal nerve pals Hypoparathyroidism hypocalcaemia Hypothyroidism Thyroid storm Tracheal obstruction due to haematoma in the wound


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