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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
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 • 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.
Primary Causes
• Autoimmune (Hashimoto’s) Thyroiditis
• Congenital hypothyroidism
• Thyroiditis
• Post surgery
• Irradiation (Radioactive iodine, Head & Neck Ca)
• Dietary Iodine deficiency
• Drug effects including anti-thyroid medication
• High amounts of Iodine eg Amiodarone
• Thyroid gland agenesis/dysgenesis
• Infiltrations – Amyloidosis, Haemochromatosis, Fibrous Thyroiditis (Reidel’s)
• Subacute (Viral), Painless (Postpartum) Thyroiditis: Transient Hypothyroidism
HYPOTHYROIDISMLow T3 and/or T4
Other Findings• 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
↑ ↓ Overt Primary Hypothyroidism
↑ → (usually low normal)
Subclinical Primary Hypothyroidism
↓ ↓ Secondary Hypothyroidism
Major Causes of Hyperthyroidism
• Graves disease• Toxic multinodular goitre• Toxic nodule• Thyroiditis• Excess replacement • TSH secreting tumour• Amiodarone• Ectopic thyroid tissue
• Trophoblasctic tumours
HYPERTHYROIDISMRaised T3 and/or T4
Other Findings• 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
Patient A Clinical Biochemistry ------------------------------------------------------------------------------
Sample collected : XX-Aug-XXRef. Range
Serum T.S.H. - - - - - <0.1 mIU/L ( 0.3 – 3.5 ) Free T4 - - - - - 50.2 pmol/L (10.0 -25.0 ) Free T3 - - - - - 22.0 pmol/L ( 3.5 - 7.5 )
1. Patient comes with weight loss and palpitations. Below is his thyroid panel.
What is your specific diagnosis?
Some Questions
Patient A Clinical Biochemistry ------------------------------------------------------------------------------
Sample collected : XX-Aug-XXRef. Range
Serum T.S.H. - - - - - 10.0 mIU/L ( 0.3 – 3.5 ) Free T4 - - - - - 13.2 pmol/L (10.0 -25.0 ) Free T3 - - - - - pmol/L ( 3.5 - 7.5 )
2. Clinical information – Cold intolerance, constipation
What is your specific diagnosis?
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 12-
24 months, then taper to see if there’s remission
S/Es: Rash, Pruritus, Arthralgias, Agranulocytosis
Pregnancy: Potassium ThioUracil(PTU)
Hyperthyroidism Rx3. RadioActive Iodine
• Oral• Concentrates in the
thyroid gland• Localised destruction• Postablative
hypothyroidism
4. Surgery
• Toxic Adenoma: Lobectomy
• Toxic MNG with compressive symptoms
KI/Lugol’s solution
• Reduces vascularity pre-surgery