Thyroid Dysfunction and Nodules Flashcards
The vast majority of metabolic thyroid disease is due to a primary abnormality of the thyroid gland itself. True or false?
True in 98% of cases
It is very rare for a pituitary adenoma to produce TSH and lead to thyrotoxicosis and pituitary failure very rarely presents with isolated hypothyroidism
This means TSH levels can be used as a screening test for hyper or hypothyroidism
What happens with regards to TSH and free T4 in hyper and hypothyroidism?
Hyperthyroidism: TSH decreased and free T4 increased
Hypothyroidism: TSH increased and free T4 decreased
What is a goitre?
Refers to a thyroid swelling
What different types of goitre are there?
Diffuse
Multinodular
Single nodule
What is the prevalence of goitre in UK?
7% of females
1% males
Not known why more common in females - the oestrogen/progesterone ratio may affect thyroid function
When can physiological goitre (normal thyroid function) occur at?
Menarche
Pregnancy
Menopause
What are the commonest causes of goitre globally?
Iodine deficiency - reduced thyroxine levels lead to increased TSH -> generalised thyroid enlargement (usually nodular)
Multi nodular goitre - cause unknown, normal thyroid function although after many years small number may develop hyperthyroidism = toxic mutinodular goitre
What is the commonest cause of goitre in UK?
Multinodular goitre
What areas are more likely to be iodine deficient?
Mountainous areas (iodine high in sea)
A goitre may accompany hyper or hypothyroidism. True or false?
True, but not necessary present in either
When is iodine deficiency a particular concern?
During pregnancy - if mother is iodine deficient and hypothyroid, then the foetus is also iodine deficient.
Leads to a child with: mental retardation, abnormal gait, deaf-mutism, short stature, goitre, hypothyroidism
What can cause hypothyroidism?
Autoimmune destruction - Hashimoto’s disease
Severe iodine deficiency
Thyroiditis
Thyroidecromy or radioactive iodine treatment
Over response to hyperthyroidism drug treatment
How many women over 30 have Hashimoto’s thyroiditis?
10%
What antibodies are present in the blood with Hashimoto’s thyroiditis?
Antibodies to thyroglobulin and thyroid peroxidase
Can you get a goitre with Hashimoto’s disease?
Yes in early stages may be associated with small diffuse goitre (due to inflammation) or the thyroid may never enlarge and shrink in size from beginning
How is hypothyroidism treated?
Oral thyroxine
Adjust dose to normalise serum TSH
What symptoms are associated with hypothyroidism?
Excessive tiredness Memory problems, depression, psychosis Weight gain Cold intolerance Gruff voice Puffy eyes, face, hands, feet Dry, flaky skin Hair loss, particularly outer 1/3 eyebrows Symptoms of carpal tunnel syndrome Constipation Menorrhagia Muscle weakness and cramps g
What signs are associated with hypothyroidism?
Weight gain
Dry skin, brittle hair, loss of outer 1/3 eyebrows
Pallor - peaches and cream face
Coarse facial features, periorbital puffiness
Bradycardia
Hyporeflexia
Non pitting oedema - myxoedema (due to deposition of polysaccharides particularly around eyes, hands, feet)
Ascites or pericardial effusion (uncommon)
What causes hyperthyroidism?
Graves’ disease
Toxic multinodular goitre
Toxic adenoma
Describe Graves’ disease
An autoimmune disease. They thyroid component is caused by a circulating immunoglobulin called thyroid stimulating immunoglobulin (TSI) - attaches to and stimulates the TSH receptor.
TSI causes all of the classical signs and symptoms of thyrotoxicosis and additional unique features of Graves :
- exopthalmos
- pre tibial myxoedema
What is exophthalmos seen in Graves?
An abnormal protrusion of the eye resulting from swelling of tissue, muscle and fat in socket behind eye
How is thyrotoxicosis treated?
Carbimazole - prevents thyroid peroxidase from coupling and iodinating the tyrosine residues on thyroglobulin, thereby reducing production of T4
Thyroidecromy
Ablative dose of radioactive iodine
What symptoms are associated with hyperthyroidism?
Overactivity, tiredness Nervousness, anxiety, insomnia Shaking, trembling Heat intolerance Increased sweating - warm, sweaty hands Palpitations Diarrhoea Amenorrhea Proximal muscle weakness
What signs are seen in hyperthyroidism?
Weight loss Warm sweaty hands Fine hand tremor Tachycardia, AF Bouncing pulse - wide pulse pressure Proximal myopathy Lid lag Staring eyes
LPS is 90% skeletal muscle and what percentage smooth muscle?
10% - supplied by sympathetic NS - overstimulation leads to staring eyes and lid lag
Is toxic multinodular goitre autoimmune?
No, so no exophthalmos or pretibial myxoedema
What is a toxic adenoma?
A single adenoma in they thyroid that produces thyroxine autonomously
Are thyroid cancers common?
No - they account for less than 1% of all cancers in UK
Do thyroid cancers cause a metabolic disturbance?
No - non functional ‘cold’ nodule
How can thyroid nodules be assessed?
Fine needle aspiration- but most are not 100% accurate so information has to be taken in conjunction with the history and examination
If there is diagnostic doubt about the thyroid nodule after FNA, what can be done?
Hemithyroidectomy
Why are lumpectomies not done on the thyroid?
If it is a malignant nodule this will not give adequate margins on the mass and it would make further surgery difficult due to scarring and put the recurrent laryngeal nerve at unacceptably high risk
What types of malignant thyroid neoplasms are there?
Papillary adenocarcinoma
Follicular carcinoma
Medullary carcinoma
Anaplastic carcinoma
What is the most common type of malignant thyroid neoplasm?
Papillary adenocarcinoma (70%)
In terms of thyroid cancer, DNA mutations can turn proto-oncogenes (promote cell growth and proliferation) into what?
Ocogenes- proteins forcing cell to always be in on position - creating tumour
In terms of thyroid cancer, DNA mutations can turn off tumour…
suppressor genes - cells dividing uncontrollably continue unchecked
Papillary adenocarcinoma is associated with what?
RET and BRAF proto-oncogene mutations
Exposure to ionising radiation of neck during childhood
Follicular carcinomas are the second most common from of thyroid cancer. True or false?
True
Follicular carcinomas are associated with countries that have…
Low iodine diets
In follicular carcinoma that tumour grows and breaks through the thyroid’s fibrous capsule. This means…
It can invade nearby blood vessels and metastasise to bones and brain in particular.
Don’t typically invade nearby lymph nodes
Medullary carcinomas (5%) arise from what?
Calcitonin regulating c cells
Where is the highest concentration of c cells?
Upper third of thyroid medulla
- so this is where medullary carcinomas are likely to originate
What causes medullary carcinomas?
Spontaneous mutation of the RET oncogene - causing single carcinoma in one lobe of thyroid
Part of inherited mutation e.g in familial medullary inherited carcinoma - may be multiple carcinomas across both lobes.
OR associated with the inherited condition: multiple endocrine neoplasia (MEN) type 2a or 2b
- screening of other organs involved in MEN syndromes is required
Under the microscope, medullary carcinomas are made up of what shaped cells?
Spindle shaped - long and skinny
In medullary carcinoma, the c cells make excessive calcitonin, which can…
Deposit between c cells - clumps of protein cause fibrous deposits called amyloid around c cells
In medullary carcinoma, c cells can produce other hormones (not just calcitonin), such as…
Seratonin
Vasoactive intestinal peptide
Anaplastic carcinoma is typically seen in who?
Older patients
In anaplastic carcinoma, do the cells look like normal thyroid cells?
No
Contain pleomorphic giant cells
Which thyroid cancer is the most aggressive?
Anaplastic carcinoma
Do anaplastic carcinomas often grow beyond the thyroid capsule?
Yes - and invade nearby structures
What are the first signs of thyroid cancer?
Solitary painless nodule in thyroid gland
Hard and immovable
Horseness and dysphagia if invade larynx, oesophagus
No signs of hyper or hypothyroidism
What signs could indicate medullary thyroid carcinoma?
Diarrhoea (vasoactive intestinal peptide)
Flushing of skin (serotonin)
How are thyroid cancers diagnosed?
Ultrasound to identify nodule
TFTs , calcitonin
Radioiodine scan
Fine needle aspiration - identify type of tumour
Who does papillary adenocarcinoma typically affect?
Young females
How are papillary, follicular and medullary carcinomas managed?
Total thyroidectomy
Followed by radio iodine therapy for papillary and follicular carcinoma
Is anaplastic disease normally too advanced for curative surgery?
Yes
How are non neoplastic nodules managed?
Can be managed conservatively unless diagnostic uncertainty
Surgery - for compressive symptoms, cosmesis or patient preference. Should aim to restrict surgery to hemithyroidectomy due to the increased morbidity from a total thyroidectomy and the need for lifelong thyroxine replacement
What benign thyroid neoplasms can occur?
Adenoma - mainly follicular
How are adenomas treated?
Require no further treatment after diagnostic hemithyroidectomy
What non neoplastic nodules are there?
Single nodule - colloid or cystic
Multinodular goitre - these are common and if they show typical features on USS do not necessarily require FNA (but any dominant nodule should have FNA)
Is FNA reliable at differentiating a follicular carcinoma from a follicular adenoma?
No - a hemithyroidectomy should be carried out for definitive histology
What complications can occur due to thyroid surgery?
Post op haemorrhage
Airway obstruction - secondary to haemorrhage or bilateral vocal cord palsy
Vocal cord palsy
Hypocalcaemia - if parathyroid glands removed
What signs and symptoms are associated with hypocalcaemia?
CATs go numb
Convulsions
Arrhythmias
Tetany
and numbness in hands, feet and around mouth (also tingling, pins and needles sensation)
Tendon reflexes hyperactive
Trousseau sign - carpal spasm on inflation of BP cuff
Chvostek sign - facial spasm on tapping inferior cheek
Reduced calcium lowers the threshold for depolarisation (calcium blocks sodium channels - inhibiting depolarisation of nerve and muscle fibres)
Tetany
What ECG changes occur due to hypocalcaemia?
QT prolongation
At risk of Torsades de pointes - type of ventricular tachycardia
