Thyroid Disease Flashcards
How much does a normal thyroid gland weigh?
25g
Majority of cases of hypothyroidism in developed world are caused by?
Hashimoto’s thyroiditis (autoimmune)
Causes of hypothyroidism?
Auto immune disease Severe iodine deficiency Dyshormogenesis (inborn errors in the formation of thyroid hormones) Anti thyroid drugs Excessive surgical resection Treatment with radioiodine Hypopituitarism (as causes reduced TSH)
What are you at increased risk of with Hashimoto’s thyroiditis?
B cell lymphoma and at higher risk of other auto-immune diseases
Most cases of hyperthyroidism is due to …
Grave’s disease
Pathogenesis of Graves and Hashimoto’s disease?
In Hashimotos auto antibodies attack the thyroid but in Grave’s they stimulate the function of the gland
Pathology of Hyperthyroid?
Gland is diffusely enlarged, gland is hyper plastic and there are numerous closely packed acini of various sizes, sometimes intra-acinar pailliform growths, colloid is absent and columnar cells
What is non-toxic goitre?
This is a simple enlargement of they thyroid gland not associated with increased secretion of thyroid hormone.
Causes of non-toxic goitre?
Not fully understood
Iodine deficiency
Dyshormonogenesis
Describe the phases of non-toxic goitre?
Diffuse hyperplasia and then nodular hyperplasia where areas of marked hyperplasia cause atrophy of intervening parenchyma.
Most common benign tumour of the thyroid?
Follicular adenoma
How do follicular adenomas usually look?
Discrete solitary masses surrounded by encapsulating collagen cuff
Most common malignant tumour of the thyroid?
Papillary carcinoma
Thyroid Papillary carcinomas spread by ________
lymphatics
Characteristic of papillary carcinomas of thyroid?
Orphan Annie nuclei (clear nuclei) and psammomma bodies
Are adenomas usually functional?
No
Causes of thyroid cancers?
Ionising radiation for papillary
Iodine deficiency for follicular
Second most common thyroid cancer?
Follicular carcinoma
Thyroid follicular carcinomas usually spread by ______
haematogenous spread to the bones and lungs
Thyroid Medullary carcinomas are derived from? So can therefore stain for?
Neuroendocrine from C-cells
Stain for calcitonin
Aggressive rare thyroid cancer?
Anaplastic carcinoma
Difference between hyperthyroidism and thyrotoxicosis?
Thyrotoxicosis- any excessive thyroid hormone production
Hyperthyroidism excessive production of thyroid hormone by thyroid gland
3 causes of diffuse goitre?
Simple- no clear cause
Autoimmune disease- hashimotos or thyrotoxicosis
Thyroiditis- de quervains
2 causes of nodular goitre?
Multinodular- hyper plastic growth common in older patients
Solitary nodules- worry of malignancy but likely to be benign or cystic or largest of multinodular
Describe multi nodular goitre?
hyper plastic growth, patients are usually older and euthyroid but may be border hyperthyroid. Most common cause of tracheal or oesophageal compression and can lead to nerve palsy. Some people may be asymptomatic. Surgery done if a structural problem or significant retrosternal extension but most can be left alone.
Small euthyroid goitres may occur in …..
puberty or pregnancy and often resolve
Describe the USS-FNA staging of solitary nodules
FNA USS Thy1 – inadequate Thy2 – Benign U2 Thy 3 (a/f) – Atypical U3 Thy4 – Prob malignant U4 Thy 5 – malignant U5
Define primary and secondary thyroid disease
Primary thyroid disease: disease affecting the thyroids gland itself, this can occur with goitre or without. Auto-immune thyroids disease is most common.
Secondary thyroid disease: hypothalamic or pituitary disease, no thyroid gland pathology
Describe the lab results in primary and secondary hypo and hyperthyroidism?
Primary hypothyroidism: Free T3/4 are low and TSH is high
Primary hyperthyroidism: Free T3/4 are high and TSH is low
Secondary hypothyroidism: Free T3/4 and TSH is low (issue with pituitary)
Secondary hyperthyroidism: Free T3/4 high and TSH high (functional tumour in pituitary)
Most common cause of hypothyroidism in developing world?
Iodine deficiency
Clinical features of hypothyroidism?
Cold skin and cold intolerance Bradycardia, dilation, worsening of heart failure Dry skin, coarse, sparse hair Decreased appetite but weight gain Constipation Macroglossia and deep voice Slow reflexes Menorrhagia later oligomenorrhoea and amenorrhea Fluid retention and oedema loss of libido
Describe investigations for hypothyroidism?
Increased TSH and decreased fT4/3 (in secondary TSH will be low)
TPO antibodies in Hashimotos
What antibodies in Hashimoto’s?
TPO
Describe management of hypothyroidism?
Replacement therapy with levothyroxine (T4) is given for life
Starting dose depends on severity, age and fitness of the patient. 100ug daily for young and fit. Start 50ug and increase to 100ug in older.
Aim of therapy is to restore T4 and TSH to normal range
Need to watch for other auto-immune endocrine diseases
There are higher thyroid requirements in pregnancy
Describe myxoedema coma, causes, presentation and treatment?
This typically effects elderly women with long standing but frequently unrecognised or untreated hypothyroidism
Get hypothermia, severe cardiac failure (bradycardia, heart block, T wave inversion, prolonged QT), hypoventilation, hypoglycaemia and hyponaetremia.
Need intensive care- ABC
Thyroxine cautiously
Nearly all cases of hyperthyroidism are due to…
Intrinsic thyroid disease (often Graves)
What is the most common cause of hyperthyroidism?
Graves autoimmune disease
In a young person with hyperthyroid think __1___
In an older person with hyperthyroid think __2___
1) Graves
2) Toxic multi-nodular goitre
Describe clinical features of hyperthyroid?
Lid lag and stare in eyes Tremor, hyperkinesis and anxiety Tachycardia, AF, hypertension, HF, palpitations Weight loss despite increased appetite Sweating Diarrhoea Oligomenorrhea Heat intolerance Loss of libido
ONLY IN GRAVES: exophthalmos (anterior bulging of the eye) and ophthalmoplegia (paralysis of muscles within and surrounding the eye), pretibial myxoedema and thyroid acropachy
Describe pretibial myxoedema and thyroid acropachy?
Specific signs of Graves disease- both quite rare and usually disease is picked up before this point
lesions on the skin in pretibial myxoedema
thyroid acropachy causes thickening of extremities and presents as clubbing, swelling and periosteal formation.
Describe investigations for a hyperthyroid?
Low TSH, high fT4/3
TRAb antibodies in Graves (thyroid stimulating hormone receptor antibody)
If no TRAb- radionuclide thyroid uptake scan done to look for toxic multi nodular goitre
Describe management of hyperthyroidism?
Anti thyroid drugs are used to decrease thyroid hormone synthesis- carbimazole is 1st line, propylthiouracil is 1st line in 1st trimester of pregnancy and second line in everyone else. Most with Graves will become euthyroid after 4-8 weeks with carbamizole then different regimes are used depending on the patient.
Symptomatic relief with beta blockers.
Radioiodine for relapsed Graves and nodular disease. This is safe and only contraindicated in pregnancy and eye thyroid disease. High risk of hypothyroidism after surgery.
Surgical treatment may be necessary if drugs and radioiodine not worked or contraindicated or need to manage nodules.
What are risks with thyroid surgery?
Hypothyroidism, hypocalcaemia and hypoparathyroidism and vocal cord paralysis due to damage of the recurrent laryngeal nerve.
Describe thyroid storm, symptoms signs and treatment?
Rapid deterioration of hyperthyroidism with hyperpyrexia, severe tachycardia, extreme restlessness, cardiac failure and liver dysfunction.
Urgent treatment: propanolol, potassium iodide, anti-thyroid, corticosteroids an supportive measures (may require ventilation)
Major life threatening side effect of anti-thyroid drugs?
Agranulocytosis (life threatening lowering of WBC)
6 causes of thyroiditis?
1) Hashimotos
2) De quervains/ subacute viral thyroiditis
3) Post partum
4) Drug induced (amiodarone and lithium)
5) radiation
6) acute suppurative thyroiditis (bacterial)
Thyroid cancer has a higher incidence in men or women?
women
Presentation of thyroid cancer?
Majority present with palpable nodes
If compressing structures- unexplained hoarse voice and sore throat, pain in neck, dysphagia, difficulty breathing.
Investigations for thyroid cancer?
Usually guided FNA of the lesion may need lymph node biopsy
No role for isotope scans, CT or MRI
Describe overview of management of thyroid cancer?
Surgery
Radioiodine therapy
Describe different surgeries for thyroid cancer and how it is decided? Post op care?
AMES score (age, metastases, extent and size) AMES low= lobectomy with isthmusectomy AMES high= sub total or total thyroidectomy Check serum calcium and correct if necessary, patient discharged on T3/4
Describe radioiodine therapy and what happens in thyroid cancer?
This is used in patients who have undergone subtotal or total thyroidectomy. Need to use rhTSH to raise TSH as this gives better results with initial scan. Radioiodine administered and then scanned 2 days later and this dictates whether go ahead. If go ahead patient given massive dose and has to wait in room until no longer radioactive.
Why do you want to stay on T4 after thyroid cancer surgery?
Need to suppress TSH as high TSH increases risk of recurrence.
What can be used as a tumour marker in follow up to thyroid surgery and radiation? Why?
Thyroglobulin can be used as it’s only produced by thyroid tissues and thyroid cancer
Describe risk of recurrence in thyroid cancer?
Risk diminishes with time (past 2yrs effectively cured as risk so low)
What are the long term effects of radioactive iodine therapy?
No long term effects except small increase in incidence of acute myeloid leukaemia but this tends to be in patients who have undergone multiple treatments (majority only undergo 1)
Prognosis of thyroid cancer?
DTC (papillary and follicular) has best prognosis of all cancers except non-melanoma skin cancer.
With radioactive iodine therapy is there evidence of increase in solid tumours or infertility or genetic abnormalities in children?
NO
Why can hyperthyroid be difficult to distinguish from hyperemesis of pregnancy?
Both may cause nausea, vomiting, warm, sweating and tachycardia as HCG has a similar effect to TSH and can increase free T4.
Treatment of hyperthyroid in pregnancy?
Propylthiouracil used in first trimester (carbimazole causes increased congenital abnormalities) and carbimazole in 2/3rd trimester (propylthiouracil has liver toxicity)
How can you get transient neonatal hyperthyroidism?
TRAb antibodies can cross the placenta and cause transient neonatal hyperthyroidism.
What needs done as soon as pregnancy is suspected in hypothyroidism?
Increase thyroxine dose
Untreated hypothyroidism in pregnancy….
increases risk of abortion, preeclampsia, abruption, post partum haemorrhage, pre term labour. It also effects foetal neuropsychological development, babies on average have 7 less IQ points.
Describe postpartum thyroiditis?
Get transient hyperthyroid followed by hypothyroid 3-4 months post partum. Most recover spontaneously and don’t need treatment. Hypothyroid phase is associated with post natal depression.
List five endocrine causes of sweating?
Hyperthyroidism Acromegaly Cushings Oestrogen Deficiency (post-menopause) Phaeochromocytoma
Describe what normal thyroid, Graves, toxic multi nodular goitre and hashimotos look like on thyroid uptake scans?
It’s testing thyroid function so if functioning more it will be darker etc
Normal: roughly even and dark grey
Graves: darker than normal almost black
TMG: lots of dark spots but not evenly black
Hashimotos: lighter than usual
Does thyroid cancer show on thyroid uptake scans?
Not really > may see cold lesions as usually they are non functioning
