Thyroid Disorders Flashcards
Thyroid anatomy
There are 2 lobes of the thyroid gland that wrap around the first tracheal ring
These then form together anteriorly at the isthmus of the thyroid gland
Superiorly to this forms the thyroid cartilage which comes to an anterior point called the laryngeal prominence
Superior to this is the hyoid bone
Thyroid embryology
Thyroid lobe descends caudal to the rest of the developing cranium
Sometimes thyroid doesnt descend and can be found in the tongue - called a lingual thyroid
Pre tracheal fascia - thyroid is within this, and attached to the laryngeal structures
If lump moves when you swallow it’s your thyroid
Clinical presentation of thyroid disease
Thyroid hormones control metabolic rate
Symptoms affected by thyroid disease - Thyroid hormones affect all systems in the body
Therefore is affects Energy Weight Temperature Heart rate Nervous system GI system Musculoskeletal Skin
If you have hypothyroidism then for whatever reason, T3 and T4 are not being produced, therefore body doesn’t get negative feedback from these so keeps producing TSH to stimulate production of this - so people who present with hypothyroidism usually have high levels of circulating TSH
If you have hyperthyroidism, then for whatever reason T3 and T4 are being over produced, this means that there is a large amount of negative feedback on the hypothalamus, therefore next to none TSH is produced - so people who present with hyperthyroidism usually have high levels of T3 and T4 and low levels of circulating TSH
Thyroid investigation
There are certain tests that can be done to map the thyroid
Can either feel it - only if it’s enlarged can be felt Or Can do thyroid ultrasound or Radio-isotope scan or CT scan or X ray
Hypothyroidism
Myxoedema - old fashioned name
clinical features -metabolism takes foot off the accelerator
symptoms - tiredness, weight gain, cold intolerance, change in appearance, depression, psychosis, joint + muscle ache, dry hair+ skin, constipation and puffy eyes
Signs - peri-orbital oedema, loss of eyebrows, dry, thin hair, bradycardia, slow-relaxing reflexes, carpal tunnel syndrome and cold peripheries
Causes of hypothyroidism - Auto-immune atrophic
Hashimoto’s thyroiditis
Post-partum thyroiditis - inflammation of thyroid within a year of birth
Dyshormonogenesis - cretinism
Medication - causing thyroid to stop working
Iodine deficiency - cant make T3 and T4
Treatment of hypothyroidism - Thyroxine replacement therapy - Levothyroxine (T4) for life
Starting dose depends on severity - 100µg for young and fit person
More caution in elderly and heart disease
Aims of treatment -Normalisation of blood tests -Takes 6-8 weeks
Resolution of symptoms
High TSH suggests under-replacement
Low TSH suggest over-replacement
Special situations in hypothyroidism
Myxoedema coma - Severe hypothyroidism usually in the elderly, when its cold in winter time - rare
Hypothermia and fluid overload in heart - pericardial effusion
50% mortality so requires high dependency treatment
Borderline or sub-clinical hypothyroidism - Low normal fT4 and high TSH
More common than severe hypothyroidism
Can be monitored until symptoms warrant treatment
Hyperthyroidism
Symptoms - Weight loss Irritability Restlessness Insomnia Malaise Itching Sweating Palpitations Tremor Muscle ache Diarrhoea
Signs - Tremor Hyperkinesis Tachycardia Atrial fibrillation Warm peripheries Hypertension Proximal myopathy Lid lag
Lid lag and lid retraction - The muscle that controls the eye lid is the Levator palpebrae superioris - which is innervated by the SNS - increased SNS activation in hyperthyroidism causes lid lag and retraction - hence the bulging eyes
Causes of hyperthyroidism - Graves disease
Nodular thyroid disease
Thyroiditis
Graves’ disease
Most common cause of hyperthyroidism
Auto-immune mediated stimulation of TSH receptor - body produces an antibody that stimualtes the TSH receptor even when TSH isn’t present therefore thyroid produces large amount of T3 and T4 hormone
Clinical signs of Graves’ disease:
Graves - opthalmopathy - eyes bulging - can be a problem as it puts pressure on the optic nerve
Graves dermopathy - antibodies also can effect skin - especially on the skin and nail beds
Nodular thyroid disease
Autonomous nodule present - can get single toil nodule - where you can treat via radioactive iodine or surgically remove it - usually 1 side is overdeveloped and the other is under developed
Can also get toxic multi nodular goitre
Thyroiditis
Inflammation of thyroid
Release of thyroxine into circulation
Viral infection - de quervain’s thyroiditis
After childbirth - post-partum
Medication - amiodarone
Treatment of hyperthyroidism
Medication
Carbimazole or Propylthiouracil (thionamides)
Beware of agranulocytosis (risk of infections)
Beta-blockers (dampen the SNS response to hyperthyroidism) for symptoms control
Surgery
If patient has side effects on medication or patient preference
Good cosmetic results in the right hands Small risk of laryngeal nerve palsy and hypocalcaemia
Radioactive iodine
Good definitive non-surgical option
Contra-indicated in pregnancy
Radiation restriction guidance after treatment
Special situations in hyperthyroidism
Thyroid crisis or ‘thyroid storm’
A rare condition with mortality 10%
Hyperpyrexia, tachycardia, cardiac failure, liver dysfunction
Needs urgent treatment on high dependency unit
Hyperthyroidism and pregnancy
In Grave’s disease antibodies produced by mother than overstimulate her thyroid can cross placenta
The baby can be born with hyperthyroidism
Requires close monitoring in pregnancy
Goitre and thyroid nodules
Thyroid cancer
Goitre means thyroid swelling - occurs 7% females and 1% in males
Types of goitre -
Diffuse goitre - its a simple goitre, usually an auto-immune thyroid disease- or could be Thyroiditis Nodular goitre - a Multinodular goitre - if a Solitary nodule then red flag symptom (more likely to be cancer)
Fibrotic goitre - Riedel’s thyroiditis - rare - Iodine deficiency, Common worldwide. Rare in UK
Red flag symptoms of thyroid cancer - History - Very young or old patient Rapid enlargement of lump in neck Hoarse voice and dysphagia Family history of thyroid cancer
Examination - Hard irregular thyroid mass
Fixed to surrounding structures
Cervical lymph nodes
Investigations to do of suspected thyroid cancer -
Thyroid ultra-sound
Fine needle aspiration
CT scan thorax and mediastinum
If cytology suggests cancer then Surgical removal and usually Prognosis is good
Thyroid surgery:
Must be done by an expert - don’t want to: damage laryngeal nerve, or take parathyroid so out as that could lead to hypocalcaemia
