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Flashcards in Thyroid Deck (37)
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1

describe location and shape of thyroid gland

Sits on trachea, two lobes joined by isthmus

2

what do parathyroid glands do

Parathyroid glands make:
Parathyroid hormone (PTH) – involved in Ca2+ metabolism

3

What does thyroid gland make

T3/T4/calcitonin

4

describe the thyroid pituitary hypothalamus axis

Hypothalamus releases
THYROTROPIN RELEASING HORMONE (TRH)
3aa pyro-Glu-His-Pro-NH2
TRH stimulates thyrotrophs in anterior pituitary to
produce THYROID STIMULATING HORMONE (TSH) or
THYROTROPIN
TSH stimulates thyroid gland to synthesize and release
thyroid hormones

5

What is the main hormone released by thyroid

mainly T4 metabolised to T3 in periphery

6

At thyroid receptors which is more potent t3 or t4

t3

7

Which hormone is involved in negative feedback of thyroid

T3 acts on the thyrotrophs to decrease release of TSH
and to decrease release of TRH from hypothalamus

8

briefly describe organisation of thyroid gland

follicles formed by throid cells, inside each follicle is a colloid. in between follicles are c cells.

9

outline how thyroid hormone is synthesised

Active uptake of iodine
Synthesis of glycoprotein THYROGLOBULIN
contains about 115 tyrosine residues
Organification of iodine by
THYROID PEROXIDASE in the presence of
H2O2
Addition of iodine to TYROSINE
Monoiodotyrosine (MIT)
Di-iodotyrosine (DIT)
MIT + DIT ------→ tri-iodothyronine (T3
)
DIT + DIT ------→ thyroxine (T4
)

10

what is the role of TPO (thyroid peroxidase)

Organification of iodine by
THYROID PEROXIDASE in the presence of
H2O2
Addition of iodine to TYROSINE

11

how does T4 travel in blood

majority is bound to TBG 75%,tbpa 20%, albumin 10%, small small amount is free

12

How does T3 travel in blood

TBG majority then albumin then minority 4% is free

13

How do thyroid hormones interact with target cells

Thyroid hormones interact with nuclear receptors
Thyroid hormone enters cells by diffusion or by specific
carrier
T3 enters the nucleus and binds to the thyroid receptor
Hormone-receptor complex binds to thyroid hormone
responsive element (TRE) on DNA

14

What physiological changes does T3 result in

Increased mRNA production
Increased protein synthesis
Increased Na+/K+-ATPase levels
Increased ATP turnover
Increased O2 consumption
Increased number of adrenoceptors

15

What does thyroid hormone conc increase do to cardiac muscle

Increase cardiac muscle contractility tachycardia

16

What does thyroid hormone conc increase do to cholesterol

Increase cholesterol degradation

17

What does thyroid hormone conc increase do to bones

Increase bone turnover

18

What does thyroid hormone conc increase do to gut

Increase gut motility

19

What does thyroid hormone conc increase do to blood

Increase erythropoeisis

20

What does thyroid hormone conc increase do to respiratory centre

Maintenance of hypoxic and hypercapnic drive in
respiratory centre

21

What does thyroid hormone conc increase do to heat and 02 consumption

Increased O2 consumption and heat production

22

What does thyroid hormone conc increase do to metabolism

Increase metabolic turnover of hormones and drugs

23

what are the effects of a hypothyroid state

increase bodyweight, decrease oxygen consumption, heat production, bmr, cns decreased (drowsy), reflexes decreased, sns (decreased), cardiac bradycardia decreased cardiac output and bp, gut effects decreased

24

Signs of hypothyroidism

weight gain, constipated,slow reflexes, Hypercholesterolaemia
hyperprolactinaemia

25

What is Hashimoto thyroiditis

autoimmune disease antibodies to thryoglobulin or thyroid peroxidase

26

what is cretinism

Failure of delivery of thyroid hormones in the foetus – cretinism

27

How do you treat hypothyroidism

Thyroxine (T4
)
T1/2 6 days, effects last 14 days
Liothyronine (sodium salt of T3
)
T1/2 2-4 days, effects last 8 days

28

How does iodine deficiency cause hypothyroidism and how is it treated

Treatment Iodine supplements
GOITROGEN - suppresses hormone secretion -
increases TSH secretion – goitre
iodine in kelp (seaweed)
brassicae (cabbage)
cassava
lithium
some local drinking water
cough mixtures
decrease intake

29

Signs of hyperthyroidism

nervous, sweating, palpitations, fatigue,weightloss, tremor, eye signs atrial fibrillation,
pre tibial myoxedma

30

what is graves disease

GRAVES’ DISEASE (diffuse toxic goitre)
autoimmune disease
TSAb (LATS) - produces prolonged stimulation of TSH
receptors