Clinical Thyroid Disease Flashcards
Name four thyroid diseases
- Hypothyroidism
- Goitre
- Thyroid Cancer
- Hyperthyroidism
How is TH release stimulated?
Hypothalamus -> anterior pituitary releases TSH -> T3 and T4
What are the key symptoms of hypothyroidism?
- Weight Gain
- Lethargy
- Feeling cold
- Constipation
- Heavy periods
- Dry Skin/Hair
- Bradycardia
- Slow reflexes
- Goitre
- Severe – puffy face, large tongue, hoarseness, coma
What are the key symptoms of hyperthyroidism?
- Weight Loss
- Anxiety/Irritability
- Heat Intolerance
- Bowel frequency
- Light periods
- Sweaty palms
- Palipitations
- Hyperreflexia/Tremors
- Goitre
- Thyroid eye symptoms/signs
What are the three different catergories of hypothyroidism?
- Primary (thyroid not producing hormone)
- Subclinical (compensated)
- Secondary (pituitary not releasing TSH to stimulate thyroid)
What is subclinical hypothyroidism?
Early, mild form of hypothyroidism - subclinical because only the serum level of thyroid stimulating hormone from the front of the pituitary gland is a little bit above normal.
What are the level of TSH and FT3/4 in hypothyroidism?
- Primary - raised TSH, low FT3+4
- Subclinical - raised TSH: normal FT3+4
- Secondary - low TSH, low FT3+4
(FT3 is triiodothyronine and FT4 is thyroxine)
Name causes of primary hypothyroidism
- Congenital
* Acquired
Describe the congenital causes of primary hypothyroidism
Developmental
• Agenesis / maldevelopment
Dyshormonogenesis
• Trapping / organification / dehalogenase
Describe the acquired causes of primary hypothyroidism
- Autoimmune thyroid disease (hashimotos / atrophic)
- Iatrogenic (post-op, external RT for head + neck cancers, antithyroid drugs, Amiodarone)
- Chronic iodine deficiency
- Post-subacute thyroiditis (post partum thyroiditis)
What are the causes of secondary /tertiary hypothyroidism?
Pituitary/hypothalamic damage: • Pit. tumour • Craniopharyngioma • Post pituitary surgery or RT • Sheehan's syndrome • Isolated TRH deficiency
What are the two main investigations for hypothyroidism?
- TSH / fT4
* Autoantibodies: TPO (thyroid peroxidase antibodies)
What are the treatment strategies for hypothyroidism?
Levothroxine (T4) tablets
• 50mcg/day, after 2 weeks increase to 100mcg
• Increase until TSH normal
What is the treatment of hypothyroidism in special situations?
- Ischaemic heart disease - start lower at 25mcg, risk of angina
- Pregnancy - increase in LT4 dose
- Postpartum thyroiditis - trial withdrawal and measure TFTs in 6 weeks
- Myxedema coma - rare emergency, may need IV T3 (steroid)
What is the treatment of subclinical hypothyroidism?
- TSH > 10
- TSH > 5 with positive thyroid antibodies
- TSH elevated with symptoms - trial therapy for 3/4 months and continue if symptomatic treatment
What are the risks of over treatment of hypothyroidism?
Osteopenia and atrial fibrillation
Describe hypothyroidism in pregnancy
• Increase levothyroxine requirements
• Inadequate treatment -> increase foetal loss and lower IQ
• Treat subclinical hypothyroidism is pregnant
• At diagnoses of pregnancy:
- Increase LT4 by 25%
- Keep TSH in low normal range and FT4 in high normal range
Name causes of Goitre
Physiological:
• Puberty
• Pregnancy
Autoimmune:
• Graves disease
• Hashimotos disease
- Thyroiditis (acute or chronic)
- Iodine deficiency (endemic goitre)
- Dyshormogenesis
- Goitrogens
What are the different types of goitre?
- Multinodular goitre
- Diffuse goitre (colloid or simple)
- Cysts
- Tumour (adenoma, carcinoma, lymphoma)
- Miscellaneous (sarcoidosis, TB)
Describe the features of a solitary nodule thyroid
Risk of malignancy
• Child
• < 30yrs but > 60yrs
• Pain, cervical lymphadenopathy
- Large dominant nodule of MNG also needs investigation
- 5% chance of malignancy
What are the investigations of a solitary thyroid nodule?
- TFT (solitary toxic nodule)
- Ultrasound (benign vs malignant)
- Fine needle aspiration!!
- Isotope scanning if low TSH (hot nodule)
What is a hot or cold nodule?
If a nodule is composed of cells that do not make thyroid hormone (don’t absorb iodine), then it will appear “cold” on the x-ray film. A nodule that is producing too much hormone will show up darker and is called “hot.”
Describe the different types of thyroid cancer
Papillary:
• Multifocal, local spread to lymph nodes
Follicular:
• Usually single lesion
• Metastases to lung/bone
What is the management of thyroid cancer?
- Poorer prognosis: age < 16 or > 45
- Near total thyroidectomy
- High dose radioiodine (ablative)
- Long term suppressive doses of thyroxine
Follow up:
• Thyroglobulin
• Whole body iodine scanning (following 2-4 weeks of thyroxine withdrawal or recombinant TSH injections)
