Case 7 - Thyroid Disease - Progress Test Flashcards
What causes thyroid hormones to be released?
- Hypothalamus secretes thyrotropin-releasing hormone (TRH)
- This stimulates the anterior pituitary to secrete thyroid-stimulating hormone (TSH)
- This stimulates the thyroid to release T3 (triiodothyronine) and T4 (thyroxine)
What do thyroid hormones do in the body?
They act on a variety of tissues to:
- help regulate the use of energy sources
- help regulate protein synthesis
- control the body’s sensitivity to other hormones
What is primary hypothyroidism caused by?
A problem with the thyroid gland
eg. an autoimmune condition
What is secondary hypothyroidism caused by?
A problem with the pituitary gland
(eg. pituitary apoplexy)
or a lesion compressing the pituitary gland
What is congenital hypothyroidism?
A problem with thyroid dysgenesis
or thyroid dyshormonogenesis
What is the main type of hyperthyroidism?
Primary hyperthyroidism
What is the most common pathology assoicatied with hypothyroidism?
Hashimoto’s thyroiditis
What is Hashimoto’s thyroiditis and what other conditions is it associated with?
An autoimmune disease
Associated with:
- type 1 DM
- Addison’s
- Pernicious anaemia
- Vitiligo
Hashimoto’s is assoicated with development of MALT lymphoma
What are the other causes of hypothyroidism?
- Subacute thyroiditis (de Quervain’s)
(causes a painful goitre and a raised ESR) - Riedel thyroiditis
(causes a painless goitre. The normal tissue is replaced by fibrous tissue) - Post-partum thyroiditis
- Drugs: lithium, amiodarone
- Iodine deficinecy
What is the most common pathology associated with hyperthyroidism?
Grave’s disease
thyroid eye disease may also be seen
What are the other causes of hyperthyroidism?
Toxic multinodular goitre
(treatment of choice = radioiodine)
Drugs: amiodarone
What are the symptoms of hypothyroidism?
- Weight gain
- Lethargy
- Cold intolerance
- Dry, cold, yellowish skin
- Dry, coarse scalp hair
- Loss of the lateral aspect of the eyebrows
- Constipation
- Menorrhagia
- Decreased deep tendon reflexes
- Carpal tunnel syndrome
What are the symptoms of thyrotoxicosis?
- Weight loss
- Manic restlessness
- Heat intolerance
- Palpitations (may provoke arrhythmias)
- Pre-tibial myxoedema
- Thyroid acropachy (clubbin)
- Diarrhoea
- Oligomenorrhea
- Anxiety
- Tremor
What would investigations for primary hypothyroidism show?
High TSH
Low free T4
What would investigations for secondary hypothyroidism show?
Low TSH
Low free T4
What would investigations for sick euthyroid syndrome show?
Low TSH
Low free T4
What would investigations for subclincial hypothyroidism show?
High TSH
Normal free T4
Would would investigation in patients with poor complicance to thyroxine show?
High TSH
Normal free T4
Would would investigations for primary hyperthyroidism show?
Low TSH
High free T4
What antibodies are seen in Graves’ disease?
TSH receptor antibodies
What antibodies are seen in Hashimoto’s thyroiditis?
anti-TPO antibodies
anti-thyroglobulin (Tg) antibodies may also be seen
What investigation would be used to diagnose toxic multinodular goitre?
Nuclear scintigraphy
Toxic multinodular goitre reveals patchy uptake
How is hypothyroidism managed?
Thyroxine
How is hyperthyroidism managed?
Propanolol for symptomatic relief
Carbimazole
Radioiodine treatment
What is the pharacology of carbimazole?
Carbimazole blocks thyroid peroxidase from coupling and iodinating the thyrosine residues on thyroglobulin - reducing thyroid hormone production
What is an important side effect of carbimazole?
Agranulocytosis (dangerously low WBC count)
How is carbimazole taken?
Taken OD for 6-9 months
Then withdrawn to see if in remission
Thyroixine is added once the patient is euthyroid
How long should you avoid contact with children and pregnant women after radioiodine treatment?
3 weeks
What complication of hyperthyroidism can be worsened by radioiodine treatment?
Thyroid eye disease
How is thyroid eye disease prevented from worsening after radioiodine treatment?
Prednisolone
How are thyroid cancers investigated?
Thyroid US
Fine needle aspiration
What are some side effects of levothyroxine?
Hyperthyroidism (due to over treatment)
Osteoporosis (reduced bone mineral density)
Worsening angina
AF
What does of levothyroxine should be given initially?
50-100mcg.
25 mcg should be given in patients over 50 and those with cardiac disese or severe hypothyroidism, and then slowly titrated up.
When should thyroid levels be checked after starting levothyroxine?
8-12 weeks
What TSH range is levothyroixine hoping to achieve?
0.5-2.5
How should a levothyroxine dose be adjusted in pregnancy?
Increase dose by at least 25-50 mcg of levothyroxine.
What medications interact with levothyroxine?
Iron
Calcium carbonate
What is subacute thyroiditis?
Thyroiditis thought to occur following a viral infection
What are the phases of subacute thyroiditis?
Phase 1 (3-6 weeks) : hyperthyroidism, painful goitre, raised ESR
Phase 2 (1-3 weeks) : euthyroid
Phase 3 (weeks to months) : hypothyroidism
Phase 4 : thyroid structure and function returns to normal
How is subacute thyroiditis investigated?
thyroid scintigraphy
Shows globally reduced uptake of iodine-131
How is subactue thyroiditis managed?
Usually self-limiting and doesn’t require treatment
Thyroid pain may respond to aspirin or NSAIDs
In more severe cases, or if hypothyroidism develops, then steroids are used
What is post-partum thyroiditis and how is it managed?
Thyrotoxicosis, followed by hypothyroidism, followed by normal thyroid function.
anti-TPO is found in 90% of cases.
Management:
- Propanolol in the thyrotoxic phase
- Thyroxine in the hypothyroid phase
What can trigger a thyroid storm?
- Surgery
- Trauma
- Infection
- Acute iodine load eg. CT contrast media
What are the clinical features of a thyroid storm?
Fever > 38.5 Tachycardia Confusion and agitation Nausea and vomiting Hypertension Heart failure Abnormal liver function tests (may be jaundiced)
How is a thyroid storm managed?
Symptomatic treatment:
- Paracetamol
- beta blockers eg. propanolol IV
Treat underlying cause
Anti-thyroid drugs:
- methimazole or
- propylthiouracil
Lugol’s iodine
Dexamathasone - 4mg IV qds
(blocks conversion of T4 to T3)
