Thyroid diseases Flashcards
What is hyperthyroidism?
Refers to overactive thyroid gland, leading to increased thyroid hormone (triiodothyorine T3 and thyroxine T4) production and secretion by the thyroid gland.
What is primary hyperthyroidism?
Refers to thyroid gland pathology causing excessive thyroid hormones.
What types of primary hyperthyroidism are there?
Overt primary hyperthyroidism
Subclinical hyperthyroidism
What does overt primary hyperthyroidism?
Refers to when TSH is below normal range AND free T4 and free T3 are above the normal range.
What does subclinical hyperthyroidism mean?
Refers to when TSH is below normal range AND free T4 and free T3 are within the normal range.
What is secondary hyperthyroidism?
Refers to pathology in the hypothalamus or pituitary.
The pituitary can produce too much TSH (thyroid stimulating hormone), which can act on the thyroid gland to produce excessive thyroid hormones.
Examples of primary causes of hyperthyroidism?
Grave’s disease
Toxic adenoma
Toxic multinodular goitre
Medications (e.g. amiodarone)
Thyroiditis
Examples of secondary causes of hyperthyroidism?
Amiodarone
Lithium
TSH producing pituitary adenoma
Choriocarcinoma (beta-hCG can activate TSH receptors)
Gestational hyperthyroidism
Pituitary resistance to thyroxine (i.e., failure of negative feedback)
Struma ovarii (ectopic thyroid tissue in ovarian tumours)
Risk factors for hyperthyroidism?
- Female
- Family history -Graves’ disease
- Smoking
- Low iodine intake
- Autoimmune disease
What is Grave’s disease?
Refers to an autoimmune condition where the immune system produces TSH receptor antibodies, which acts on the TSH receptors on the thyroid, causing primary hyperthyroidism.
What is thyroiditis?
Refers to thyroid gland inflammation.
Often causes hyperthyroidism at the beginning, then hypothyroidism.
What is thyrotoxicosis?
Refers to excessive quantity of thyroid hormones circulating in the body due to any cause, including hyperthyroidism.
How does hyperthyroidism present? Presentation of Grave’s disease?
↑ Basal metabolic rate
Heat intolerance
Tachycardia and arrhythmias
Weight loss
Diarrhoea
Sweaty skin
Insomnia and sleep disturbances
Restlessness and tremors
Goitre (depending on cause)
Both hyper- and hypothyroidism can lead to:
- mood changes
- depression, anxiety
- menstrual disturbances
Grave’s disease:
- Exophtalmos (proptosis) (bulging eyes)
- Pretibial myxoedema (Looks discoloured, waxy, oedematous appearance)
- Lid lag
- Thyroid acropachy: Soft tissue swelling in extremities, nail clubbing, and periosteal new bone growth
What investigations would you do for hyperthyroidism?
FBC
LFTs
Inflammatory markers -ESR and CRP.
TFTs
- raised fT4 (free thyroxine)
- raised FT3 ( free triiodothyronine)
- low TSH
Blood tests for thyroid antibodies
- Thyroid peroxidase antibodies (TPOAbs; if a woman is postpartum and potential diagnosis of postpartum thyroiditis)
- TSH-receptor antibodies (TRAbs; Grave’s disease)
US of the neck
Radioiodine uptake test
- test measures the thyroid’s ability to take up radioactive iodine
How to manage overt hyperthyroidism?
Emergency admission:
- if symptoms suggest serious complication (e.g. thyrotoxic crisis)
Urgent referral to endocrinologist:
- if pituitary or hypothalamic disorder
Endocrinologist referral:
- has a goitre, nodule, or structural change in the thyroid gland
- suspected malignancy (TFTs are usually normal in thyroid cancer)
While awaiting specialist assessment, offer:
- beta blocker (propranolol; relief of symptoms (palpitations, tremor, tachycardia, or anxiety)
- carbimazole →first-line anti-thyroid drug if BB is not helping or not tolerated. [propylthiouracil preferred in pregnant women or planning pregnancy]
- Amiodarone or lithium
When is thyroidectomy (surgery) offered?
Grave’s disease if compression or malignancy suspects OR if other tx unsuitable.
Toxic multiple or single nodule present and radioactive iodine is unsuitable.
How to manage subclinical hyperthyroidism?
Urgent referral using suspected cancer pathway:
- has a goitre, nodule, or structural change in the thyroid gland
- suspected malignancy (TFTs are usually normal in thyroid cancer)
Endocrinologist referral:
- If two TSH readings are <0.1 mU/L at least three months apart AND evidence of thyroid disease
How is Grave’s orbitopathy managed?
Emergency admission or ophthalmologist:
→ if suspected sight-threatening complication such as:
- dysthyroid optic neuropathy
- globe subluxation
- corneal exposure (cornea or sclera is visible when eyes are closed)
Smoking cessation
Use of artificial tears to lubricate the eyes.
Avoid irritation and damage to the eyes.
Elevate the head of the bed to relieve morning eyelid swelling.
How is Grave’s disease managed?
Propranolol (blocks adrenergic effects)
Carbimazole (antithyroid drug)
- start 40mg
- gradually reduce dose to maintain euthyroid
- 12-18 month tx course
- risk of agranulocytosis
If the above does not work, then:
- Carbimazole 40mg
- Take levothyroxine once the pt is euthyroid
- tx lasts 6-9 months
Radioiodine tx
- used if other tx doesn’t work
- contraindicated in pregnancy, age <16, thyroid eye disease
- majority become hypothyroid and require levothyroxine for following 5 yrs.
What is thyroid storm?
Refers to a rare life-threatening emergency
caused by untreated or inadequately managed hyperthyroidism.
Can occur following stressful illness, thyroid surgery, or radioactive iodine.
How does thyroid storm present?
Restlessness
Agitation
High-output heart failure
Severe tachycardia
Fever
Dehydration
Vomiting
Delirium and altered mental status
How is thyroid storm managed?
Emergency treatment (high mortality)
IV fluids, propranolol, hydrocortisone, oral iodine
Carbimazole or propylthiouracil
Radioactive iodine (I-131); thyroidectomy once patient is euthyroid
Complications of hyperthyroidism?
Thyroid eye disease
Atrial fibrillation
High-output heart failure
Osteopenia/Osteoporosis
Upper airway obstruction
Thyroid cancer
Thyroid storm
What is thyroid neoplastic disease?
Refers to papillary carcinoma is the most common thyroid cancer.
How does thyroid neoplastic disease present?
Enlarging thyroid nodule (painless)
Hoarseness
Difficulty swallowing
‘Cold nodule’ on scan [nodules that collect less radioactive material than the surrounding thyroid tissue are considered “cold”]
What investigations would you do for thyroid neoplastic disease?
- TFTs
- USS
- FNA (fine needle aspiration)
- radioactive iodine scan
How is thyroid neoplastic disease diagnosed?
TFTs are often normal
USS -nodule characteristics
FNA -cytology
Radioactive iodine scan -reveals COLD nodule
How is thyroid neoplastic disease managed?
Total or partial thyroidectomy +/- iodine-131 ablation
Then LT4 replacement (levothyroxine)
How is thyroiditis managed?
Aspirin, bedrest, +/- steroids
Steroids are given dependent on each hospital and how unwell the patient is.
Steroids help regulate body’s balance of water and electrolytes by promoting fluid retention.
Monitor thyroid levels -will often become hypothyroid before returning normal within 6 months.
Thyroiditis tends to reoccur and the patient is at increased risk of developing thyroid disease in the future.
What are the rules for radioactive iodine tx?
- Women must not be pregnant or breastfeeding and must not get pregnant within 6 months of tx
- Men must not father children within 4 months of tx
- Limit contact with people after the dose, particularly children and pregnant women
Causes of thyroiditis?
De Quervain’s (subacute) thyroiditis
Hashimoto’s thyroiditis
Postpartum thyroiditis
Drug-induced thyroiditis (e.g. amiodarone, interferons, lithium, and cytokines)
What is Hashimoto’s thyroiditis?
Refers to a transient thyrotoxicosis in acute phase and is common in women.
What is De Quervain’s (subacute) thyroiditis?
Refers to a transient inflammatory thyroid disease (temporary inflammation of the thyroid gland) that is associated with pain and tenderness of the gland.
Three phases:
- thyrotoxicosis
- hypothyroidism
- return to normal
First phase: painful goitre (lump or swelling at front of the neck due to swollen thyroid), raised ESR and CRP (inflammatory markers), flu-like illness (fever, aches, fatigue), and excessive thyroid hormones.
Self-limiting condition, NSAIDs (help pain and inflammation), beta blockers (hyperthyroidism symptoms), levothyroxine (hypothyroidism symptoms)
What is postpartum thyroiditis?
Refers to a woman’s thyroid becoming inflamed after giving birth.
