Transcript Thyroid Function Tests

Thyroid Function Tests
Orishaba Diana
And
Enoch T
Introduction to the Thyroid Gland
• Objectives
• Explain the synthesis and regulation of thyroid
hormone production
• Describe the actions of thyroid hormones
• Describe the etiology, major symptoms and
pathophysiology of hyper and hypothyrodism
• Understand the role of thyroid hormone
measurement in the management of thyroid disease
Control of thyroid hormone production
Peripheral tissues
Metabolic Effects of Thyroid Hormones
•Effects on the function of virtually every organ
system
•Maintain metabolic stability and increase resting or
basal metabolic rate
•Increase heart rate
•Increase mental alertness
•Maintain GI motility & bone turnover
•Brain dev’t and skeletal maturation during foetal
development
• Thyroid hormones regulate:
- Growth and development
- Temperature
- Oxygen consumption
- Metabolism of carbohydrate, protein and
lipid
- TSH secretion
Thyroid disease
• Can be Hypothyroidism or Hyperthyroidism. Either way,
this can be a primary disease of the thyroid gland or
secondary to brain lesions.
• TFTs alone can differentiate the above.
• Other Ix are important for specific causes eg
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Anti-thyroid antibodies (Anti-peroxidase) –in hashimoto’s
thyroiditis, titre tells likelihood of progression to overt
hypothyroidism.
TSH receptor antibodies – Grave’s
CT scan in brain lesions
Radio iodine nuclide studies etc
• NB: Goitre refers to thyroid swelling and can be both in
patients with hypothyroidism, euthyroidism or
hyperthyroidisim.
HYPOTHYROIDISM
Low T3 and/or T4
Primary Causes
• Autoimmune (Hashimoto’s)
Thyroiditis
• High amounts of Iodine eg
Amiodarone
• Congenital hypothyroidism
• Thyroid gland
agenesis/dysgenesis
• Thyroiditis
• Post surgery
• Irradiation (Radioactive
iodine, Head & Neck Ca)
• Dietary Iodine deficiency
• Drug effects including antithyroid medication
• Infiltrations – Amyloidosis,
Haemochromatosis, Fibrous
Thyroiditis (Reidel’s)
• Subacute (Viral), Painless
(Postpartum) Thyroiditis:
Transient Hypothyroidism
Other Findings
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Anaemia
Hyponatremia
Elevated triglycerides & Cholesterol
Sinus bradycardia
Pericardial effusion
ECG: Low voltage
Slow relaxation of deep tendon
reflexes
Diagnosing Hypothyroidism
Insidious onset, so recognition is sometimes
difficult.
Always remember the Negative Feedback Loop:
TSH
Free T4/T3
Diagnosis
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↓
Overt Primary Hypothyroidism
↑
→ (usually low
normal)
Subclinical Primary Hypothyroidism
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↓
Secondary Hypothyroidism
HYPERTHYROIDISM
Raised T3 and/or T4
Major Causes of Hyperthyroidism
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Graves disease
Toxic multinodular goitre
Toxic nodule
Thyroiditis
Excess replacement
TSH secreting tumour
Amiodarone
Ectopic thyroid tissue
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Trophoblasctic tumours
Other Findings
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Increased appetite
Weight loss
Resting tremor
Wide pulse pressure
Flow murmur
Proximal muscle weakness
Brisk deep tendon reflexes
Diagnosing Hyperthyroidism
• Try to identify the underlying cause, because
treatments vary
• Use Hx, physical exam, Imaging, antibody tests,
etc
• Always remember the negative feedback loop
TSH
Free T4/T3
Diagnosis
↓
↑
Overt primary
hyperthyroidism
↓
→
Subclinical primary
hyperthyroidism
↑
↑
Secondary
hyperthyroidism
• TSH (0.3-3.5 mU/L)
• Free T4 (10-25 pmol/L)
• Free T3 (3.5-7.5 pmol/L)
Some Questions
1. Patient comes with weight loss and palpitations.
Below is his thyroid panel.
What is your specific diagnosis?
Patient A
Clinical Biochemistry
-----------------------------------------------------------------------------Sample collected : XX-Aug-XX
Ref. Range
Serum
T.S.H. - - - - - <0.1
Free T4 - - - - - 50.2
Free T3 - - - - - 22.0
mIU/L ( 0.3 – 3.5 )
pmol/L (10.0 -25.0 )
pmol/L ( 3.5 - 7.5 )
2. Clinical information – Cold intolerance, constipation
What is your specific diagnosis?
Patient A
Clinical Biochemistry
-----------------------------------------------------------------------------Sample collected : XX-Aug-XX
Ref. Range
Serum
T.S.H. - - - - - 10.0
Free T4 - - - - - 13.2
Free T3 - - - - -
mIU/L ( 0.3 – 3.5 )
pmol/L (10.0 -25.0 )
pmol/L ( 3.5 - 7.5 )
Hypothyroidism Treatment
• Depending on the cause but usually is thyroid
replacement using Levo thyroxine
Hyperthyroidism Rx
1. Beta Blockers
 Sympathomimetic blockers
 Propranolol also inhibits
peripheral conversion of T4
to T3
 Sole Tx in transient
thyrotoxicosis
2. Antithyroid drugs:
Thionamides eg CARBIMAZOLE
 Inhibit thyroid hormone synthesis
 Can induce remission in Grave’s
disease
 Control thyrotoxicosis before
radioiodine or surgery
 In Grave’s: Keep on drugs for 1224 months, then taper to see if
there’s remission
 S/Es: Rash, Pruritus, Arthralgias,
Agranulocytosis
 Pregnancy: Potassium
ThioUracil(PTU)
Hyperthyroidism Rx
3. RadioActive Iodine
4. Surgery
• Oral
• Concentrates in the
thyroid gland
• Localised destruction
• Postablative
hypothyroidism
• Toxic Adenoma:
Lobectomy
• Toxic MNG with
compressive symptoms
KI/Lugol’s solution
• Reduces vascularity presurgery
Conclusion
Interpretation of TFT’s
TSH
T4
T3
Primary
hypothyroisism
High
low
low
Secondary
hypothyroidism
Primary
hyperthyroidism
low
low
low
Low
high
high
high
high
high
Secondary
hyperthyroidism