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BIOM2012 > Endocrine > Flashcards

Endocrine Flashcards

1
Q

Which is the most active form of thyroid hormone

A

T3

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2
Q

Which is the predominant form of thyroid hormone in the plasma

A

T4

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3
Q

What cells make up the thyroid gland

A

Follicle cells

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4
Q

What is colloid

A

Colloid is an extracellular fluid space found in the follicle cells where it contains predominantly thyroglobulin which is required for thyroid hormone synthesis

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5
Q

What is hyperthyroidism, causes and symptoms

A

Overactive thyroid gland. producing too much thyroid hormones. Graves disease, hypersectreting thyroid tumour and secondary to excess of TSH and TRH. Sweating in normal temperatures, excessive weight loss, elevated metabolic rate, heart palpitations, muscle weakening, bulging of eyes commonly seen in graves disease.

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6
Q

What is hypothyroidism, causes and symptoms

A

Inactive thyroid gland secreting too little thyroid hormones. Hashimoto autoimmune thyroiditis, secondary to deficiency in TSH and TRH, inadequate supply of dietary iodine. Excessive weight gain due to decrease metabolic rate, sensitive to cold, easily fatigure due to lack of ATP, weak pulse, slow mentation and reflexes.

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7
Q

What is pinocytosis, name a cell that uses this method

A

Follicle cells, uses this method during the secretion process of TG structures in the colloid into the cell.

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8
Q

What enzyme is essential for the formation of MIT and DIT from iodide and thyroglobulin

A

Thyroid peroxidase

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9
Q

How does T3 and T4 leave the follicle cells

A

They are lipophilic in nature so they are able to leave the follicle cell and travel to other organs

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10
Q

Describe the formation of TG vesicles

A

Amino acids are used to synthesis TG and it travel through the golgi and forms TG vesicles and is released out of the atypical membrane into the colloid

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11
Q

How is iodide taken up from the blood stream and released into the colloid

A

Taken up from the blood stream via Na/I cotransporter through active transport into follicle cells and exits through another transporter, pendrin

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12
Q

what are the 2 important components to form thyroid hormones

A

phenyl rings-derived from tyrosine residues and iodine taken up from diet

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13
Q

What is the hypothalamus-pituitary-thyroid axis

A

The hypothalamus released Thyrotropin releasing hormones which stimulated anterior pituitary to release TSH which acts on the thyroid glands by binding to the TSH receptor of follicle cell which stimulates the production of thyroid hormones. The presence of these hormones in the circulation will cause a negative feedback to the TRH neurons of Hypothalamus and Tyrotrophs of the Anterior pituitary.

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14
Q

What are the key functions of TSH

A
  1. increases the follicle cell size, cell number
  2. increases follicle cell formation - thyroid gland bigger
  3. TIPP - trap iodide, iodination of tyrosine on thyroglobulin and stimulates thyroid peroxidase, pinocytosis of colloid and proteolysis of TG
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15
Q

How are most T3 synthesized

A

They are synthesized mainly through deionidation of T4 in the hepatocytes not throught TSH

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16
Q

How does T4 get converted to T3

A

T4 is deionised by iodinase into T3

17
Q

How does T3 cause gene transcription

A

It binds to the Thyroid hormone receptor in the nucleus which is bind to cofactor retinoid X receptor which is bounded to the thyroid response element

18
Q

How does T3 and T4 effect metabolic rates - give eg.

A

Increases metabolic rate through calorigenic effect - stimulates o2 consumption in most cells which increase metabolic rate and heat production. Also in skeletal muscles too much TH means muscle wasting, too little muscle weakening

19
Q

How does T3 and T4 affect growth and development

A

essential for normal somatic cells growth and neural devleopment esp in myelination of nerves

20
Q

What is the cardio response when Thyroid hormones is released?

A

Increases response to catecholamines via increases expression of adrenoreceptors and stimualtion of downstream cellular events which increases HR and force of contraction

21
Q

Name the 4 sections of the adrenal glad starting from the outer most layer

A

Z. glomerulosa, Z. fasciulata, Z. reticularis and medulla

22
Q

What hormones can be found in each section of the adrenal gland

A

Z.G - aldosterone released by angiotenisoogen for water retention. Z.F - cortisol released by ACTH in pituitary for stress. Z.R - sex steroid for reproduction also ACTH. Medulla - epinephrine and nor, for fight and flights, SNS

23
Q

Name the types of steroid hormones and an example

A

Glucocortocoids - cortisol, Sex steroids - Testosterone and Mineralcorticoids -aldosterone

24
Q

What is the precursor of steroid horomones

A

Cholesterol

25
Q

How is cholesterol synthesized

A

Synthesized throught cells from acetate or LDL uptake via LRL-mediated endocytosis

26
Q

What is the immediate precursor of cholesterol and enzyme responsible for the process

A

Preogenolone and cytochrome P-450scc

27
Q

What is cytochrome p-450scc

A

It is a rate limiting enzyme, a side chain cleavage enzyme that can be found in the inner mitochondrial membrane

28
Q

Where can the conversion system of cholesterol to steroid hormones be found?

A

It can be found in adrenal cortex, ovarian follicle -thecal cells and the testes - leydig cells

29
Q

Does free cortisol or bounded cortisol affect negative feedback response

A

Free cortisol

30
Q

what are the symptoms of cushing syndrome

A

thin extremities/ muscle wasting/ osteoporosis/ obesity / - abdominal straie/ easy bruising/ Hyperglycemia

31
Q

Symptoms of Addisons disease

A

Hypoglycaemia/ dehydration/ shock and confusion

32
Q

What are the endogenous causes of cushing syndrome

A

Tumour in pituitary - adenome benign or tumor in adrenal gland which causes abnormal z. fasciulata cell growth - increases ACTH production. Abnormal sources of ACTH - small cell lung tumor

33
Q

What are the exogenous causes of Cushing syndrome

A

Steroids medication - have the same structure as cortisol and can mimic actions on various tissue resulting in negative feedback of cortisol resulting in insufficeint stimulation resulting in atrophy. despite decrease in endogenous cortisol does not make up for the huge increase in exogenous (meds) cortisol levels

34
Q

What is addison’s disease

A

Adrenal insufficiency - failure in producing sufficient steroid hormones due to an autoimmune disease whcih destroys the adrenal cortex

BIOM2012 (1 decks)

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