Thyroid - Basic Science & Investigations

Question 1

Which important structure lies postero-laterally to the thyroid gland?

Answer 1

Carotid sheaths

Question 2

Where are the parathyroid glands in relation to the thyroid gland?

Answer 2

Posterior

Question 3

Which important structure lies medially to the thyroid gland?

Answer 3

Recurrent laryngeal nerve

Question 4

Where does lymph from the thyroid gland drain to?

Answer 4

Deep cervical nodes

Question 5

From what type of epithelium are the thyroid follicles formed?

Answer 5

Cuboidal

Question 6

What is the area in the centre of each thyroid follicle known as?

Answer 6

Colloid

Question 7

What is the name of the protein on which thyroid hormones are synthesised and stored, which is found in the colloid?

Answer 7

Thyroglobulin

Question 8

What are the spaces between thyroid follicles formed of?

Answer 8

Parafollicular ‘C’ cells

Question 9

What substance is required for the synthesis of thyroid hormones?

Answer 9

Iodine

Question 10

After T3 and T4 are formed, where are they stored until they are required?

Answer 10

Thyroglobulin (within the colloid)

Question 11

Which is the more biologically active thyroid hormone?

Answer 11

T3

Question 12

Which thyroid hormone is produced in the greatest quantity?

Answer 12

T4

Question 13

T4 is converted to T3 in which peripheral tissues?

Answer 13

Liver, kidney, muscle

Question 14

What is the process known as by which T4 is converted into T3?

Answer 14

5-monodeiodination

Question 15

1% of T4 molecules undergo the process of 3-monodeiodination to form what?

Answer 15

rT3 (the inactive reverse of T3)

Question 16

Which deiodinase enzyme is the major determinant of generating T3 from T4?

Answer 16

Deiodinase 2 (D2)

Question 17

What two hormones are responsible for the release of T3 and T4? Where are these secreted?

Answer 17

Thyrotropin-releasing-hormone (TRH) secreted from the hypothalamus and thyroid-stimulating-hormone (TSH) secreted from the anterior pituitary gland

Question 18

The majority of T3 and T4 in the circulation are bound to which protein?

Answer 18

Thyroxine binding globulin

Question 19

Why is T3 faster acting than T4?

Answer 19

It is bound less avidly to plasma proteins

Question 20

What effect does the release of T3 and T4 have on the production of TRH and TSH?

Answer 20

Negative feedback

Question 21

Are thyroid hormones released in response to high or low temperatures?

Answer 21

Low

Question 22

What effect does stress have on thyroid hormone production?

Answer 22

Reduced thyroid hormone production

Question 23

Describe the natural circadian rhythm of thyroid hormone levels?

Answer 23

Levels are high late at night and low in the morning

Question 24

What do parafollicular ‘C’ cells of the thyroid gland produce? What is the effect of this?

Answer 24

Calcitonin - lowers serum calcium (by inhibiting its release from bone)

Question 25

Individuals on which drugs should have their TFTs screened every 6 months?

Answer 25

Lithium and amiodarone

Question 26

Low TSH with high free T3/T4 is suggestive of what?

Answer 26

Primary hyperthyroidism

Question 27

High TSH with low free T3/T4 is suggestive of what?

Answer 27

Primary hypothyroidism

Question 28

High or normal TSH with high T3/T4 is suggestive of what?

Answer 28

Secondary hyperthyroidism

Question 29

Low or normal TSH with low T3/T4 is suggestive of what?

Answer 29

Secondary hypothyroidism

Question 30

The phenomenon of a raised TSH with a raised T3/4 is very rare. If it occurs, what is the most likely underlying cause?

Answer 30

TSH secreting pituitary adenoma

Question 31

TFTs with a picture of secondary hypo/hyperthyroidism suggests that the underlying problem is where?

Answer 31

Hypothalamus or pituitary gland

Question 32

What happens to the TFTs in individuals with sick euthyroid syndrome?

Answer 32

Everything is low

Question 33

What is the first line imaging investigation for the thyroid gland?

Answer 33

Ultrasound

Question 34

What investigation is needed in addition to ultrasound to determine between benign and malignant thyroid nodules?

Answer 34

FNA

Question 35

Describe what is meant by hot, warm and cold thyroids on radioisotope scanning (scintigraphy)?

Answer 35

Hot = hyperfunctional, warm = normal, cold = hypofunctional

Question 36

Which type of nodule on scintigraphy is more likely to be malignant: hot or cold?

Answer 36

Cold (20% are malignant)

Question 37

The phenomenon of a low TSH with a low T3/4 is very rare. If it occurs, what is the most likely underlying cause?

Answer 37

Pan-hypopituitarism

Question 38

What describes sub-clinical thyroid disease?

Answer 38

Abnormal TSH levels with normal thyroid hormone levels and no obvious symptoms

Question 39

Low TSH with a normal T3/T4 is suggestive of what?

Answer 39

Subclinical hyperthyroidism

Question 40

High TSH with a normal T3/T4 is suggestive of what?

Answer 40

Subclinical hypothyroidism

Question 41

When patients have subclinical hyperthyroidism, there is a risk of progression to overt hyperthyroidism, most likely caused by what?

Answer 41

Toxic multinodular goitre

Question 42

Subclinical hyperthyroidism is often associated with what two complications?

Answer 42

AF and osteoporosis

Question 43

The risk of progression from subclinical hypothyroidism to overt hypothyroidism is much increased if what is present?

Answer 43

Anti-TPO antibodies