7. Thyroid Disease - Hyperthyroidism

Question 1

What would you expect the TFT to show in someone with hyperthyroidism

Answer 1

low TSH

high T3 and T4

Question 2

what would you expect the TFT to show in someone with primary hypothyroidism

Answer 2

high TSH

low T3 and T4

Question 3

what would you expect the TFT to show in someone with secondary hypothyroidism

Answer 3

low TSH

low T3 and T4

Question 4

What antibodies are usually present in graves disease and hashimotos thyroiditis

Answer 4

antithyroid peroxide (anti-TPO) antibodies (against the thyroid gland itself)  in hashitmotos 
Antithyroglobulin antibodies - TSH receptor antibodies in graves disease

Question 5

what is graves disease

Answer 5

autoimmune condition where TSH receptor antibodies cause primary hyperthyroidism
these are abnormal antibodies produced by the immune system and mimic TSH

Question 6

In a radioisotope scan to investigate hyperthyroidism and thyroid cancers what conditions give the characteristic clinical finding

1. diffuse high uptake of the isotope
2. focal high uptake of the isotope
3. ‘cold’ areas (ie abnormally low uptake) of the isotope

Answer 6

1. graves disease
2. toxic multinodular goitre and adenomas
3. thyroid cancer

Question 7

define Hyperthyroidism and what is it also known as

Answer 7

over production of the thyroid hormone by the thyroid gland

aka thyrotoxicity

Question 8

What is the difference between primary and secondary hyperthyroidism

Answer 8

primary is due to thyroid pathology (the thyroid itself is behaving abnormally)
secondary is as a result of overstimulation by TSH and the pathology is in the hypothalamus or pituitary

Question 9

what is the most common cause of hyperthyroidism

Answer 9

Graves disease

Question 10

what is toxic multi nodular goitre (aka plummers disease )

Answer 10

nodules develop on the thyroid gland that act independently of the normal feedback system and continuously produce excessive thyroid hormone

Question 11

What is exophthalmos

Answer 11

bulging of the eyeball out of the socket caused by graves disease. Due to inflammation, swelling and hypertrophy

Question 12

what is pre-tibial myxoedema

Answer 12

deposits of mucin under the skin on the anterior aspect of the leg
specific to graves disease and is a reaction to the TSH receptor antibodies

Question 13

Describe where the thyroid gland is located and the basic structure

Answer 13

• soft gland in the lower neck, anterior to the trachea, below the thyroid cartilage of the larynx, moves when you swallow
• makes thyroxine (T4) and T3 and is composed of 2 lobes and an isthmus

Question 14

What other conditions could present with weight loss and what questions would you ask

Answer 14

• GI symptoms: anorexia, abdo pain, diarrhoea, symptoms of IBD, coeliac disease, peptic ulcer
• Symptoms of depression: low mood, loss of interest, sleep disturbances
• Symptoms of eating disorder: decreased food intake, self-induced vomiting, over exercise. Anorexia nervosa and bulimia may commonly present in this age group (early 20s)
• Polyuria and polydipsia: type 1 diabetes mellitus may present with weight loss
• Drug use: including alcohol, cocaine, amphetamines, cannabis
• Night sweats or fevers: although malignancy is rare in this age group, lymphomas may present with weight loss. TB and HIV can also present this way

Question 15

Describe the basic histology of the thyroid gland

Answer 15

• Made up of follicles lines by cuboidal epithelium and parafollicular C cells that secrete calcitonin
• follicles are filled with colloid (looks pink)
• follicular cells make thyroglobulin

Question 16

what are c cells involved in

Answer 16

the production of calcitonin involved in bone mineral deposition

Question 17

what are adjacent to thyroid gland

Answer 17

parathyroid glands

Question 18

Describe the basics of T3 and T4 production

Answer 18

• they are thyroninies that are made from thyroglobulin
• TFC make thyroglobulin under the control of TSH
• Iodine is trapped by TFC and transported into the colloid
• thyroid peroxidase in the follicular cells (TFC) iodinates tyrosine
• thyroglobulin hydrolysed and T4 is released into the blood by thyroid binding globulins
• T4 deiodinated into T3 which is more active and binds to DNA (transcriptional effects)
• T3 is 10X more active than T4

Question 19

What is the overall effect of T3

Answer 19

increased metabolic rate 8

Question 20

Describe the pituitary-thyroid hormone axis

Answer 20

• negative feedback of T4/T3 on pituitary TSH and hypothalamic TRH
• Low T4 –> increased TSH
• high T4 –> suppressed TSH
• TSH released from anterior pituitary

Question 21

In clinical practice we measure the free T4 so not that significant but what things will raise the thyroid binding globulin, increasing TBG-T4

Answer 21

pregnancy and OCP

Question 22

Name some common drugs that can affect hormone levels

Answer 22

Amiodarone (anti-arrhythmic medication)
Lithium (anti-psychotic)
Interferon (hep C treatment)

Question 23

What are the top 3/4 common causes of thyrotoxicosis

Answer 23

Graves disease
multi nodular goitre
solitary toxic nodule (solitary benign adenoma)
Drugs such as interferon (hep C treatment) and amiodarone ( anti-arrhythmic)
{thyroiditis in the very early stages cause this usually causes hypothyroidism)

Question 24

what are the cardiovascular effects of thyrotoxicosis

Answer 24

Higher pulse and BP

Can get atrial fibrillation and this is a 3X risk in the over 60s

Question 25

What are the universal features of hyperthyroidism

Answer 25

``` anxiety and irritability sweating and heat intolerance tachycardia (palpitations; AF) weight loss (despite good appetite) fatigue frequent loose stools sexual dysfunction ``` Graves disease features (see next question)

Question 26

what are the unique features of graves disease

Answer 26

``` Diffuse Goitre (without nodules) Graves eye disease - chemosis (swelling of the conjunctiva) - peri-orbital odema bilateral exophthalmos (aka proptosis) pretibial myxoedema ```

Question 27

What features are unique of toxic multi nodular goitre

Answer 27

goitre with firm nodules most patients are aged over 50 second most common cause of thyrotoxicity (after graves)

Question 28

what is a solitary toxic thyroid nodule

Answer 28

single abnormal nodule is acting along to release thyroid hormone nodules are usually benign adenomas treated with surgical removal

Question 29

what is De Quervain's thyroiditis

Answer 29

viral infection with fever, neck pain and tenderness, dysphagia and features of hyperthyroidism - there is a hyperthyroid phase followed by hypothyroid phase (due to negative feedback) - self limiting condition and supportive treatment with NSAID and beta blockers is all that is needed

Question 30

What is thyroid storm

Answer 30

this is rare presentation of hyperthyroidism that is a thyrotoxic crisis - pyrexia, tachycardia and delirium - requires admission for monitoring - may need supportive care with fluid resuscitation, anti-arrhythmic medication and beta blockers

Question 31

What are the main treatments for hyperthyroidism

Answer 31

``` Carbimazole 1st line (CBZ) - once a day Propylthiouracil 2nd line (PTU)- 3 times a day Radioactive iodine Beta-blockers Surgery ```

Question 32

Why is Carbimazole preferred over Propylthiouracil

Answer 32

There is a small risk of severe hepatic reactions, including death, with PTU

Question 33

what is the difference between 'titration-block' and 'block and replace' when treating with Carbimazole

Answer 33

titration-block is where you carefully titirate to maintain normal levels block and replace is where the dose is enough to block all production and the patient takes levothyroxine titrated to effect

Question 34

What are the strict rules that must be followed when taking radioactive iodine

Answer 34

must not be pregnant and can't get pregnant within 6 months of having it must avoid close contact with children and pregnant women for around 3 weeks (dose dependant) limit contact with anyone for several days after receiving the dose

Question 35

why might beta-blockers be given in patents with hyperthyroidism

Answer 35

- to block he adrenaline related symptoms - propranolol is a good choice as it is non-selective - don't treat the underlying problem but control the symptoms whist the treatment has time to work

Question 36

when titrating the initial dose of 40 mg of CBZ what should the subsequent doses go down in

Answer 36

5-10 mg decrements for 18-24 months

Question 37

in the block replace method using CBZ, at what point do you stop the 40mg dose and switch to levothyroxine and at what dose

Answer 37

100 mcg when T4 levels are normal and then this dose can be adjusted (note that cannot be pregnant whilst doing this)

Question 38

What is the main reg flag issue with using anti-thyroid drugs and what do you need to explain to the patient

Answer 38

- neutropenia and agranuulocytosis which is when you stop making neutrophils - need to give patients written warning advise which includes that the patient needs to report signs of infection, especially a sore throat - if this occurs then anti-thyroid drug should be stopped and antibiotics should be given in hospital

Question 39

myth busted: dose radioactive iodine treatment cause cancer or infertility

Answer 39

no doesn't cause infertility but there is a risk of radiation so say not to become pregnant till 6 months after treatment there is no excessive risk of developing thyroid cancer either

Question 40

what are the main complications with radioactive iodine

Answer 40

can get neck discomfort and can precipitate graves ophthalmopathy

Question 41

what are the main risks with a subtotal or near-total thyroidectomy

Answer 41

``` may get permanent parathyroid damage 2-4% vocal cord paralysis less than 1% bleeding less than 2% keloid scar hypothyroidism is inevitable ```

Question 42

what can cross the placenta and stimulate tithe thyroid gland of the foetus

Answer 42

thyroid stimulating antibodies in graves disease