8/3/2019 Collated Thyroid Pbl
1/13
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.
http://bestpractice.bmj.com.ezproxy.lib.monash.edu.au/best-practice/monograph/263/resources/references.html#ref-6http://bestpractice.bmj.com.ezproxy.lib.monash.edu.au/best-practice/monograph/263/resources/references.html#ref-6http://bestpractice.bmj.com.ezproxy.lib.monash.edu.au/best-practice/monograph/263/resources/references.html#ref-8http://bestpractice.bmj.com.ezproxy.lib.monash.edu.au/best-practice/monograph/263/resources/references.html#ref-8http://bestpractice.bmj.com.ezproxy.lib.monash.edu.au/best-practice/monograph/263/resources/references.html#ref-8http://bestpractice.bmj.com.ezproxy.lib.monash.edu.au/best-practice/monograph/263/resources/references.html#ref-8http://bestpractice.bmj.com.ezproxy.lib.monash.edu.au/best-practice/monograph/263/resources/references.html#ref-68/3/2019 Collated Thyroid Pbl
2/13
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
8/3/2019 Collated Thyroid Pbl
3/13
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
8/3/2019 Collated Thyroid Pbl
4/13
8/3/2019 Collated Thyroid Pbl
5/13
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
8/3/2019 Collated Thyroid Pbl
6/13
8/3/2019 Collated Thyroid Pbl
7/13
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
8/3/2019 Collated Thyroid Pbl
8/13
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
[ ]
8/3/2019 Collated Thyroid Pbl
9/13
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
8/3/2019 Collated Thyroid Pbl
10/13
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
8/3/2019 Collated Thyroid Pbl
11/13
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)
8/3/2019 Collated Thyroid Pbl
12/13
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
8/3/2019 Collated Thyroid Pbl
13/13
Top Related