Week 3 - H - Online tutorials - thyroid

Question 1

What is the butterfly shaped endocrine organ?

What does it sit anterior to?

Answer 1

Thyroid gland

Sits anterior to the trachea

Question 2

The gland moves on swallowing as it is attached to the thyroid cartilage and the upper end of the trachea

What attaches the thyroid gland to the cricoid cartilage at the upper end of the trachea?

Answer 2

Posterior suspensory ligament - the berry ligament

Question 3

What are the two different kind of cells that make up the thyroid gland?

Answer 3

The follicular cells and the parafollicular cells (C-cells)

Question 4

What produces the substance thyroglobulin?

Answer 4

The follicular cells

Question 5

What cells take up iodine from the blood?

What does the iodine act on via what enzyme?

Answer 5

The follicular cells take up the iodine and the iodine joins to the tyrosine residues on the thyroglobulin via the enzyme thyroid peroxidase

Question 6

How are the thyroid hormones produced from the thyroglobulin?

Answer 6

Lysosomes act on the thyroglobulin in the follicular cells releasing the thyroid hormones via diffusion into the bloodstream

Question 7

What are the names of the two thyroid hormones produced in the follicles and where are they stored until required?

Answer 7

T3 - tri-iodothyronine
T4 - thyroxine

Stored in the colloid until required by the body

Question 8

The majority of secreted hormones is triiodothyronine

True or false

Answer 8

False

Question 9

T3 and T4 are both hydrophilic molecules

True or false?

Answer 9

False - both hydrophobic

Question 10

Thyroid hormones work in conjuction with growth hormone when controlling metabolism
What are two other key things they have a role in?

Answer 10

Bone turnover
and

Thermogenesis

Question 11

What are the three main roles of growth hormone when acting on fat tissue, liver and muscle tissue?

Answer 11

When acting on fat, increases lipolyis to increase plasma fatty acids
When acting on liver increases gluconeogenesis to increase plasma glucose

When acting on muscle, increases protein synthesis and decrease plasma amino acids

Question 12

How do thyroid hormones increase responsiveness to neurotransmitters such as adrenaline and noradrenaline?

Answer 12

It achieves this by increasing the number of receptors

Question 13

What can hyperthyroidism do to a persons behaviour?

What can hypothyroidism do to a females menstrual cycle /sex drive?

Answer 13

Can make them agitated / always on edge

Can cause a woman to have oligomenorrhea/amenorrhea due to the increased prolactin because of the increased TRH and decrease their sex drive as the reproductive organs are slowed down

Question 14

What is the TSH receptor antibody produced in grave’s disease which prevents the thyroid from stopping producing T4 and T3 hormones?

Answer 14

TSI - thyroid stimulating immunoglobulin - acts in the same way as TSH

Question 15

Is obstructive sleep apnoea found in patients with hyper or hypo thyroidism?

Answer 15

Patients with hypothyroidism

Question 16

What test is done that screens for 9 different rare but serious conditions in children? one of the conditions is congenital hypothyroidism

Answer 16

Guthrie test

Question 17

Guthrie tests is also known as the Heel prick test

If congenital hypothyroidism is found to be positive, what is done?

Answer 17

baby is given thyroxine to help with normal development

Question 18

What does the absence of thyroxine after 3 months of age lead to?

Answer 18

leads to permanent developmental delay cretinism

Question 19

How does prolactin lead to oligo/amenorrhea?

Answer 19

Prolactin inhibits the release of FSH which will prevent the production of oestrogen required for ovulation

Question 20

How do carbimazole and propylthiouracil work to treat hyperthyroidism?

Answer 20

Both drugs inhibit thyroid peroxidase from attaching the iodine to tyrosine residues on thyroglobulin, thus preventing formation of MIT & DIT (mono-iodotyrosine and di-iodotyrosine)

(Carbimazole is a pro-drug as after absorption it is converted to the active form, methimazole. Methimazole prevents thyroid peroxidase enzyme from iodinating and coupling the tyrosine residues on thyroglobulin)