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Bio regulatory systems 2 > Thyroid Gland > Flashcards

Thyroid Gland Flashcards

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1
Q

What is Myxodema Coma?

A

As a result of sever untreated hypothyroidism

Symptoms;receding hairline, puffy face and eyes, swollen food, overgrown toenails, bad feet

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2
Q

Describe the thyroid gland?

A

butterfly shaped

around the trachea

made up of 2 lobes which are seperated by the ISTHMUS

Pyramidal lobe- embrylogical remenent of the thyrpoid that only 10-30%of people have.

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3
Q

What is the thyroid gland made up of on a cellular level?

A

Made up of multiple follicles which are made up of a spherical colloid and a layer of follicular cells around the colloid

Colloid-mucus

Also have a parafollicular cells- responsible for secreting calcatonin which is important in calcium metabolism

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4
Q

What other structures are close to the thyroid gland? Why is it important to know these?

A

Important to know these because it means when you carry out operations on the thyroid you have to be aware of the possible risks to surrounding structures and if the risk is worth the benefit

Superior and Inferior parathyroid gland on each lobe of the thyroid so there are 4 in total- important in calcium metabolism so if you remove and damage them it could cause big consequences

Recurrent laryngeal nerve- supplies the vocal cords- damage can effect voice

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5
Q

How does the thyroid gland develop?

A

Starts at the back of the tongue at the base from the floor of the pharynx

Then you develop a duct called the THYROGLOSSAL DUCT which is what your thyroid tissue descends upon, this then divides into 2 lobes and the duct disappears leaving the FORAMEN CAECUM which is just a remenant

Final position of gland is by week 7 , thyroid then develop

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6
Q

What can happen if the thyroid gland doesn’t develop properly?

A

If it doesn’t descend beyond the tongue you could have a LINGULAR THYROID-just a nodule at the back of the throat

But if you remove this you may be removing the only thyroid tissue that someone has which could cause bigger problems

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7
Q

What happens in the colloid?

A

thyroid hormone is made here

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8
Q

How is thyroid hormone made?

A

1- TSH is secreted from the anterior pituitary gland

2- Blood vessel surround the follicular cells and the TSH comes via the blood and binds to TSH receptor on the Follicular cells

3-Iodide ions arrive and are transported into the cell via sodium iodide transporter

4- Iodide then crosses the cell and enters the colloid

5-Iodide is then oxidised to make IODINE

6-The binding of the TSH also begins the production of THYROGLOBULIN which is a prohormone that has tyrosine residues in its structure. TYROSINE is an amino acid that has the capablility of been iodinated(meaning you can add an iodine group to it)

7- When TSH arrived it also activated an enzyme called THYROPEROXIDASE which travels into the colloid and along with hydrogen peroxide it catalyses the iodination reactions that occur within the colloid

8- iodine sticks onto tyrosine residues and produces monoiodothyronine(MIT) if 1 iodine is added and diiodothyronine(DIT) if 2 iodines are added

9-MIT +DIT couple to give T3 which is an active thyroid hormone and DIT+DIT couple to give T4 which is an unactive thyroid hormone

10- The T3 and T4 are still stuck to the thyroglobulin so move back into the follicular cell where protein bonds are broken, and then they are released from the thyroglobulin and enter blood circulation

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9
Q

Why is the position where the iodine binds on the thyroglobulin important?

A

Because if you change the position where the iodine binds you could get reverse T3 which is inactive

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10
Q

Why is T4 useful?

A

It can be used to make T3 as deiodonase enzymes remove an iodine from T4 to produce T3 80% of T3 is produced this way

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11
Q

How does thyroid hormone get around the body?

A

Mostly bound to plasma proteins:

-Thyroid binding globulin:TBG (70-80%)

Albumin(10-15%)

Prealbumin(transthyetin)

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12
Q

What happens when T4 enters a body cell?

A

1- turned to T3 by deiodinase enzyme

2-T3 enters the nucleus and binds to the thyroid hormone receptor

3- This results in altered gene expression and does what its supposed to do

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13
Q

What are 5 functions of Thyroid hormone(T3)?

A

Thyroid hormone binds to nuclear receptors leading to the synthesis of new proteins that are:

essential for fetal GROWTH and development particularly of the brain and CNS

Increase BASAL METABOLIC RATE- This is how fast your cells are working, the amount of energy each cell needs to function. Does this by increasing O2 consumption, Heat production, Na+/K+ ATPase effects

METABOLISM of nutrients-Increased glucose absorption, glycogenesis, lipolysis, gluconeogenesis, protein synthesis and degradation

Can effect the sympathetic Nervous system causing CARDIOVASCULAR effects by potentiating the action of CATECHOLAMINES which can lead to increased heart rate(tacycardia) and increased cardic output

Have effects on the GI, CNS, Reproductive systems(women can lose periods and suffer with fertility problems)

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14
Q

What happens to the thyroid of a pregnant woman?

A

The feutus take thyroid from the mother as thyroid hormone can cross the placenta

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15
Q

What is congenital hypothyroidism?

A

Where baby cannot produce its own thyroid when born because they have NO THYROID GLAND- It is fine when it is in utero as it takes thyroid hormone from the mother.

This results in CRENTINISM

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16
Q

What test is carried out on a newborn child to test for Thyroid problems?

A

HEEL PRICK TEST- measures TSH levels and if these levels are high this tells you the baby is not producing enough thyroid hormone (which is why lots of TSH is being secreted in an attempt to increase the production of thyroid hormones)

17
Q

Describe the hyper-thalamo pituitary thyroid axis?

A

1-Hyperthalamus produces hormone called TRH

2-TRH then enters the anterior pituitary via portal circulation where it stimulates the thyrotroph cells to release TSH

3- TSH then enters systemic circulation where it arrives at the thyroid

4-This then results in the production of T3 AND T4

5-Once these made they signal back to the hyperthalamus and anterior pituitary to stop making the TSH AND TRH so production stops(negative feedback) This is the hyperthalamo pituitary thyroid Axis

18
Q

What does somatostain do?

A

Negatively inhibits TSH production from the anterior pituitary

19
Q

What is the effect of giving someone to much iodide?

A

Can inhibit the production of T3 and T4

Doctors use this to prevent the production of these hormones in people with an overactive thyroid by giving them POTASSIUM IODIDE

20
Q

In which sex is thyroid disease most common?

A

Women 4:1 ratio

We think its something to do with auotimmuntity

May produce antibodies that effect the thyroid gland that could potentially destroy it something to do with how our immune systems have had to adapt to pregnancy and antigens of a feutus that we have to contend with

Therefore we are more susceptible to autoimmune diseases which cause most thyroid diseases

21
Q

Is an overactive or underactive thyroid more common?

A

They are equally common

22
Q

What causes primary hypothyroidism?

A

AUTOIMMUNE damage to the thyroid-causes thyroxine levels to decline and TSH levels to climb(in an attempt to raise thyroxine levels)

SURGERY-if thyroid removed

23
Q

What is another name for T4

A

thyroxine

24
Q

What are the commonest forms of autoimmune thyroid disease?

A

Hashimotos thyroiditis-hypothyroidism

Graves Disease- Hyperthyroidism

The presence of one autoimmune disease no matter what kind can increase the risk of others and therefore increases the risk of autoimmune related thyroid problems

25
Q

Why would someone with vitaligo be more at risk of thyroid disease?

A

Vitaligo is an autoimmune disease.

The presence of one autoimmune disease no matter what kind can increase the risk of others and therefore increases the risk of autoimmune related thyroid diesease

26
Q

What are the symptoms and signs seen in a patient presenting with hypothyroidism?

A
  • Deepening voice
  • Depression and tiredness
  • Cold intolerence
  • Weight Gain and reduced appetite
  • Constipation
  • Bravcucardia
  • Eventual myxoedoma coma
  • enlargement of the thyroid gland (Goitre)
  • Memory impairment
  • Swoolen face, swelling of the eye socket
  • Dry rough skin
  • Paraesthesia
  • Muscle cramps
  • Deminished fertility
  • Low sexual desire
  • Menstrual cycle disorders
  • Shaggy hair and hair loss
27
Q

What tablet is used to help with hypothyroidism? How does it work?

A

LEVOTHYROXINE- You take it for the rest of your life and your absolutely fine

It is just the drug form of T4. Eventhough T4 is inactive it converted to T3 naturally in the body by deiodinase enzymes

28
Q

Why would you give someone with Hyperthyroidism Levothyroxine?

A

-First you would give them a drug that stops the production of thyroxine altogether and then you would give them the amount of levothyroxine they would need so they produce a normal amount of thyroxine

very rarely used

29
Q

In what form and dosage is levothyroxine given?

A

Usually given in a tablet form

Only given in IV form in emergencies situations like myxodema coma and in this case T3 is given as there is no IV preparation of T4

Usually start with dose of 100 micrograms- might start lower in elderally

You ADJUST the dose according to the TSH level(aim to get it back into the normal range)

30
Q

What are the potential complications of Levothyroxine?

A
  • Given too much causes weight loss
  • some people claim it gives headaches
  • In major complications if you give too much you could have tacycardia or heart attack
31
Q

Why dont you give T3 the active version to hypothyroid patients?

A
  • expensive
  • doesn’t give added benefits over T4
  • body naturall converts levothyroxine(T4) to T3 anyway
32
Q

What happens when given a combination of T3 and T4?

A

some reported i-ii–improvement in wellbeing but it is thought that this is physcological as there is no evidence of added benefit -It can be toxic as often patients start taking T3 despite only being prescribed T4 therefore they get toxic symptoms -palpatations, tremour, anxiety and often TSH is often supressed suggesting there is too much hormone around

33
Q

What happens when you have hyperthyroidism?

A
  • Thyroxine levels rise too much
  • TSH levels drop in an attempt to decrease levels of thyroxine
34
Q

What are the 3 main causes of Hyperthyroidism?

A

Graves disease- gland becomes smoothly enlarged and OVERACTIVE

-Toxic multinodular goitre- multiple nodules in thyroid, the combined effect of the nodules all releasing thyroxine means too much is released

-single nodule in thyroid which just overproduces thyroxine

35
Q

Describe 3 clinical presentations of Graves disease?

A

SMOOTH GOITRE-Some people make antibodies that bind to and stimulate the TSH receptor in the thyroid, this causes a smooth goitre(thyroid enlarged)

EXOPHTHALAMAS-other antibodies bind to muscles behind the eye = bulging of the eyeballs where there is white around the whole of the iris

-PRETIBIAL MYXOEDEMA-thickening and growth of the skins of the shins

36
Q

What are the symptoms and signs of Hyperthyroidism?

A
  • Heat loss
  • Weight loss with increased appetite
  • Myopathy
  • Modd swings
  • Diarrhoea
  • Tremor of the hands
  • Palpitations
  • Sore, bulging eyes
  • Goitre
  • Broken hair, hair loss, Nervousness, irratibility, depression
  • increased heart rate, high bp, arrhythmia
  • Muscle cramps and weakness
  • warm moist skin, increase body temperature
  • Cycle disorders

Bio regulatory systems 2 (15 decks)

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