Thyroid Flashcards
Recall the physiology of the thyroid gland
TSH causes an uptake of iodide, and thyroid peroxidase turns iodide into iodine. TSH then binds iodine to thyroglobulins to form thyroxine, and thyroxine is released.
How is the hypothalamus and the pituitary associated with the thyroid?
The hypothalamus releases TRH, which acts on the pituitary. The pituitary releases TSH which acts on the thyroid. T4 give negative feedback to the hypothalamus and the pituitary.
What is hypothyroidism?
A lack of thyroxine, underactive thyroid
What are the clinical features of hypothyroidism?
- Reduced basal metabolic rate (weight gain)
- Cold hands
- Constipation
- Dysmenorrhoea and infertility
How should you investigate hypothyroidism?
- Blood TSH and T4
- Other autoimmune conditions
What are the causes of hypothyroidism?
Autoimmune
- Hashimoto’s Thyroiditis (anti-thyroid peroxidase autoantibodies)
- Primary atrophic hypothyroidism
Other
- Iodine deficiency
- Post thyroidectomy/radioiodine
- Drug induces (amiodarone, lithium)
What is subclinical hypothyroidism? What is this associated with?
A high TSH with a normal T4
This is associated with hypercholesterolaemia
How do you manage hypothyroidism?
Check ECG to rule out CVD
Thyroxine replacement (levothyroxine) depending on BMI
50/125/200 mcg a day
What is hyperthyroidism?
An overactive thyroid
What can cause hyperthyroidism?
High uptake
- Grave’s disease (TSH receptor autoantibodies)
- Toxic multinodular goitre
- Toxic adenoma
Low uptake
- De Quervain’s thyroiditis
- Postpartum thyroiditis
What are the features of hyperthyroidism?
- Increase basal metabolic rate (weight loss)
- Palpitations, AF
- Diarrhoea
- Dysmenorrhea and infertility
If Graves:
- Exophthalmos
- Smooth goitre
How do you investigate a case of hyperthyroidism?
- TSH
- Free T4
- Other autoimmune diseases
What is the management of hyperthyroidism?
- Beta blockers for heart rate
- Radioiodine
- Carbimazole (if unresponsive to radioiodine)
- Thyroidectomy (then thyroxine replacement)
What is the most common thyroid neoplasia? What is the epidemiology surrounding it, how do you treat it and what is the prognosis?
Papillary (60%) of cases., usually in ages 30-40. It is treated with surgery, and carries an excellent prognosis.
What are the thyroid neoplasia, in order of most common.
- Papillary (60%)
- Follicular (25%)
- Medullary
- Lymphoma
- Anaplastic
Describe follicular thyroid cancer
Usually middle aged, well differentiated and surgery is used to treat
Describe medullary thyroid cancer
Originates in the parafollicular C cells
Either:
- Linked to MEN2
- Familial
Describe thyroid lymphoma
5% of all thyroid cancer cases, and has a MALT origin. Is precipitated by long standing Hashimoto’s disease
Describe anaplastic thyroid cancer
Usually affects the elderly and is generally unresponsive to treatment; poor prognosis
How can you investigate thyroid cancer?
Thyroglobulin is a marker of cancer cells
- Use to confirm diagnosis
- Use to confirm remission
What is subclinical hyperthyroidism?
Where the T4 is normal but the TSH is low. This may progress to primary hypothyroidism.
