MEH Thyroid

Question 1

Where do you find the thyroid gland in relation to the thyroid cartilage (Adams apple)?

Answer 1

Posterior. It’s on the cricoid cartilage

2/3rd ring of trachea

Question 2

The two lobes are joined by an …

Answer 2

Isthmus

Question 3

Where do you find the parathyroid glands?

Answer 3

On the posterior of the thyroid gland.

These are distinct glands

Question 4

What do the thyroid glands produce (2)?

What do the parathyroid glands produce (1)?

Answer 4

Thyroid hormone (T4/Thyroxine/tetraiodothyronine) and (T3/triiodothyronine) produced in the follicular cells

Calcitonin is produced in the parafollicular cells. It reduces the calcium in the blood and offsets the effects of parathyroid hormone

Parathyroid (chief cells) produce parathyroid hormone

Question 5

Where is thyroid hormone produced?

Answer 5

In the thyroid follicles

Thyroid follicles are made up of thyroid cells that form a circle with COLLOID (a deposit of thyroglobulin)

Question 6

What is the important enzyme involved in thyroid hormone production?

What 3 reactions does it cause?

Answer 6

THYROID PEROXIDASE

1) Oxidation of Iodide to iodine
2) Addition of Iodine onto tyrosine residues on thyroglobulin
3) Coupling of MIT/DIT to form thyroid hormones within thyroglobulin protein

Question 7

Name 3 foods were you find iodine?

Answer 7

Fish
Iodised salt
Milk (not organic), cheese,
Eggs

Question 8

Name the transporter that gets iodide into the centre of the thyroid follicles.

1)

2)

Answer 8

Sodium Iodide symporter

Pendrin

Question 9

T3 v T4

Which is more biologically active?
Which is more commonly secreted
Where is T4 converted to T3 in the body?
How is T3/4 carried in the blood?

Answer 9

T3
T4 = 90%
Liver and Kidney
Thyroxine-binding globulin

Question 10

In the thyroid axis which does the hypothalamus produce?

What does the _________ pituitary produce?

Answer 10

Thyroid releasing hormone (TRH) - Rolf Harris is RELEASED from prison)

Thyroid stimulating hormone released from the ANTERIOR PITUITARY

Question 11

What two hormones are released from the POSTERIOR pituitary?

Answer 11

Vasopressin (ADH)

Oxytocin

Question 12

In the thyroid hormone axis.. What has a positive feedback effect and what has a negative feedback effect?

Answer 12

Positive
TRH +> Ant Pituitary
TSH +> Thyroid Glands
T3/4 +> Target organs

Negative
TSH -> Hypothalamus
Thyroid hormone -> Ant pituitary and hypothalamus

Question 13

TSH is a trigger for Thyroid hormone release. What type of GPCR does it activate

Answer 13

Gas and Gaq

PKA, PKC, Ca2+ all stimulate the synthesis and release of thyroid hormone

Question 14

What are the 3 general effects of thyroid hormone

Answer 14

1) Increase Basal metabolic rate and heat production
- Increase mitochondria size and number
- Stimulating respiratory chain enzymes

2) Stimulate Metabolic pathways
- Lipid metabolism (Lipolysis and B-oxidation of fatty acids)
- Carbohydrate metabolism (stim insulin-dependent entry of glucose to cells, Increase gluconeogenisis and glycogenolysis

3) Sympathomimetic effects

Question 15

Thyroid hormone effects of CVS? (2)

Answer 15

Increase CO (HR and force of contraction)
Peripheral vasodilation

Question 16

Thyroid hormones effect on nervous system?

Answer 16

Increase myelination

Question 17

What type of receptor are thyroid hormone receptors?

Answer 17

Nuclear receptors

Question 18

Is thyroid hormone lipid soluble?

Answer 18

Yes

Question 19

Does thyroid hormones repress or relive repression of gene transcription?

Answer 19

Relieves repression

Question 20

What is a goitre?

Is it caused by hypo or hyperthyroidism?

Answer 20

A goitre is a enlargement of the thyroid gland

Caused by both Hypo and hyper

Question 21

Name 5 symptoms of HYPOTHYROIDISM?

Answer 21

Obesity
Lethargy (lack of energy)/Tiredness
Intolerance to cold
Bradycardia
Constipation
Slow reflexes
Dry skin
Alopecia

MENORRHAGIA

Question 22

Name a disease that can cause HYPOTHYROIDISM

Answer 22

Hashimotos disease

Autoimmune - destruction of thyroid follicles
Most common disease of thyroid gland
More common in women
Goitre may or may not be present

Question 23

Hypothyroidism in

Infants.. causes?

Adults..causes?

Answer 23

Infants - cretinism

Adults - myxedema (dermatologenous display of hypothyroid symptoms - puffy skin, muscle weakness, slow speach, mental deterioration, intolerance to cold

Question 24

What is the main cause of hyperthyroidism

Answer 24

Graves’ disease

Question 25

Name 5 symptoms of hyperthyroidism?

Answer 25

Tachycardia
Weight loss
Heat intolerance
Fatigue and weakness
Increased bowel movements
Sweating and tremor
Hyper-reflexive
Breathlessness

Question 26

What is Graves’ disease?

Answer 26

Autoimmune disease that causes a toxic multinodular goitre

Caused by the production of THYROID STIMULATING IMMUNOGLOBULIN (TSI)

TSI continually stimulates Thyroid hormone secretions

Question 27

+T3, +T4, –ve TSH

Answer 27

Graves’ disease

Question 28

Name a drug used to treat hypo/hyper thyroidism?

Answer 28

CARBIMAZOLE - block thyroid hormone

It’s a pro-drug and gets converted into its active form of Methimazole

Question 29

How can you distinguish between a goitre and a thyroglossal duct cyst?

Answer 29

A thyroglossal duct cyst moves up on tongue protrusion

Question 30

When can physiological goitres occur?

Answer 30

Menarche (first period)
Pregnancy
Menopause

Question 31

What is the commonest cause of goitres globally?

1st?
2nd?

Answer 31

Iodine deficiency

Multinodular goitre (can become toxic, then causes hyperthyroidism). MOST COMMON IN THE UK