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week 11 Flashcards

1
Q

What can hypothyroidism be treated with?

A

levothyroxine
30mins before breakfast and caffeine containing liquids.
liothyronine
carbimazole

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2
Q

Where are thyroid hormones produced?

A

thyroid gland by the thyroid follicles

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3
Q

Colloid

A

proteinaceous depot of thyroid hormone precursors

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4
Q

Synthesis of thyroid hormones

A

1) Iodine co-transported with Na+.
2)Diffusion into follicle cell.
3)Iodine transported to colloid, oxidized and attached to rings of tyrosine’s in TG. (thyroglobulin)
4)Iodinated ring is added to a DIT at another spot.
5)Endocytosis of TG
6)Lysosomal enzymes release T3 and T4 from TG.
7)T3 and T4 are released from cell

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5
Q

What is the most active thyroid hormone?

A

T3

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6
Q

How is T4 changed to T3

A

deiodination

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7
Q

How is thyroid hormone secretion controlled?

A

Hypothalmus———————————————————–
Thyrotophin-releasing hormone TRH secretion I
Anterior pituitary—————————————————–
Thyroid-stimulating hormone TSH secretion I Thyroid gland I
Thyroid hormone (secrettion) ———————————-
Targtet cell responce

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8
Q

Euthyroid state

A

Thyroid hormone secretion is normal

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9
Q

Hypothyroid state

A

Thyroid hormone secretion is subnormal

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10
Q

Hyperthyroid state

A

Thyroid hormone secretion is excessive

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11
Q

Actions of thyroid stimulating hormone

A

stimulate T3 and T4 production
increases protein synthesis
increases DNA replication and cell division
increases rough endoplasmic reticulum and cell machinery required for protein synthesis.

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12
Q

What causes a goitre?

A

hypothyroidism, hyperthyroidism and euthyroidism, excessive exposure to TSH.

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13
Q

Actions of T3 and T4 hormones

A

T4 secreted to T3
Increased basal metabolic rate, heat production, growth and development, maintenence of normal activity

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14
Q

What are the effects of an iodine deficiency?

A

Metal retardation, reduction in physical growth, deaf-mutism, cretinism (rare)

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15
Q

Iodine RDA

A

150 mcg/day

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16
Q

TSH and T4 levels in correspondance to;
Normal
Hyperthyroidism
Hypothyroidism primary
Hypothyroidism secondary

A

TSH normal T4 normal
TSH low T4 high
TSH high T4 low
TSH low T4 low

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17
Q

Signs and symptoms of hypothyroidism

A

cold intolerance, weight gain, tiredness, bradycardia, constipation, depression, pale dry skin, puffy face

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18
Q

Hashimoto’s thyroidism

A

autoimmune disorder and the main cause of hypothyroidism.
Self-reactive T lymphocytes recruit B cells and T cells into the thyroid.
B cells produce antibodies of thyroid epithelial cells. T cells become cytotoxic T lymphocytes leading to cells destruction and decreased production of the thyroid hormones.
T4 decreases and TSH increases

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19
Q

Is Hashimotos more common in men or women?

A

twice as prevalent in women

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20
Q

Treatment of Hashimoto’s/primary hypothyroidism. Side effects?

A

Levothyroxine - synthetic T4.
Hair loss, headaches, sleep problems, nervousness, fever, pounding heart, appetite changes

Liothyronine - synthetic T3.
Risks of osteoporosis and heart arrythmia.
shorter half-life

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21
Q

Secondary hypothyroidism

A

uncommon
pituitary doesn’t produce TSH or hypothalamus doesn’t produce sufficient TRH.
T3 T4 and TSH are below normal

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22
Q

What may happen as a result of untreated hypothyroidism?

A

Myxoedema coma
extreme hypothermia (24-32C), seizures, respiratory depression

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23
Q

Drugs effecting thyroid function

A

Corticosteroids - decreased production of TRH and TSH
Lithium - inhibits release of T3 and T4
Amiodarone - contains iodine and can cause hypo and hyperthyroidism
Cholestyramine - reduces absorption of thyroxine

24
Q

Signs of hyperthyroidism

A

heat intolerance, palpitations, weight loss, restlessness, fatigue, sweating, frequent bowel movement, goitre

25
Cause of hyperthyroidism
thyroid produces excess of T4, reduction in TSH due to negative feedback loop. T3 also elevated.
26
Graves disease
most common cause of hyperthyroidism caused by TSI - thyroid stimulating immunoglobulin which increases secretion of thyroid hormones autoimmune disease
27
Treatment of hyperthyroidism
Surgery, radioactive iodine - administered orally.
28
Antithyroid drugs
Thioamides (carbimazole, propylthiourcail) inhibit thyroid peroxidase and prevent hormone synthesis. Effect of onset is slow - increased risk of infection.
29
What is the difference in chemical structure of T3 and T4
T4 has an extra iodine
30
How are T4 and T3 transported around the body?
Bound to proteins in the blood.
31
Levothyroxine logP and pKa
logP 7.4 and pKa 10, 9 ,4
32
Liothyronine logP and pKa
LogP 6 pKa 10,9,4
33
How does carbimazole work?
a prodrug in which the active form inhibits thyroid peroxidases which convert tyrosine into MIT and DIT. = no T3 and T4. Log P of carbimazole 0.3, LogP of methimazole -0.3.
34
Hormones secreted by the adrenal glands.
Adrencorticoids, minerlacorticoids, glucocorticoids, sex hormones, adrenaline, noradrenaline
35
What are mineralocorticoids? Give example
Aldosterone Made in Zona glomerulosa Important for Na+ reabsorption and K+ excretion in kidneys.
36
What are glucocorticoids? Give example
Cortisol Made in the Zona fasciculata Regulate body's response to stress, also help regulate glucose levels.
37
What are sex hormones? Give example
Androgens Synthesized in Zona reticularis Regulate reproductive function
38
What is cortisol secretion controlled by?
hypothalamic pituitary adrenal axis
39
Cortisol secretion
stress hypothalamus -------------------------------------------------------- corticotrophin-releasing hormone (CRH) secretion I anterior pituitary --------------------------------------------------- adrenocorticotrophic hormone (ACTH) secretion I adrenal cortex I cortisol ----------------------------------------------------------------- target cell response
40
Factors increasing cortisol production
sleep deprivation, trauma, extreme fasting
41
When does cortisol release peak values?
upon waking - diurnal variation
42
Cellular actions of cortisol
increases circulating glucose levels maintains responsiveness of blood vessels to vasoconstrictive stimuli can have anti-inflammatory action
43
What effect does an increased level of cortisol have of plasma levels of glucose, fatty acids and amino acids
increases them
44
What is Addison's disease?
adrenocortical insufficiency primary adrenal insufficiency due to destruction or dysfunction of the adrenal cortex, effects both mineral and glucocorticoid function.
45
Symptoms of Addison's disease.
darkening of the skin extreme fatigue weight loss and reduced appetite low blood pressure GI distrubance salt craving low blood glucose
46
Causes of Addison's disease
Infections, invasion, haemorrhage
47
What impact does Addison's disease have on the cortisol flow chart?
decreased secretion of cortisol due to negative feedback increased secretion of corticotrophin releasing hormone and adrenocorticotrophic hormone.
48
What is it that causes hyperpigmentation in Addison's disease?
increased levels in adrenocorticotrophic hormones that constantly stimualte melanocytes.
49
Treatment of Addison's
Hydrocortisone (sometimes prednisolone or dexamethasone) 15-30mg Fludrocortisone (mineralocorticoid)
50
Secondary adrenal insufficiency and treatment
Lack of ATCH secretion from pituitary Don't show hyperpigmentation or salt craving. Can occur if glucocorticoid medication is stopped too abruptly Treatment; glucocorticoid e.g. hydrocortisone, mineralocorticoid is unnecessary as the gland itself is not damaged.
51
Tertiary adrenal insufficiency
Lack of corticotrophin releasing hormone secretion from the hypothalamus
52
How do glucocorticoid drugs work?
Suppress hypothalamus and anterior pituitary. Anti-inflammatory's = predinsolone, dexamethasone, hydrocortisone, beclamethasone
53
Adrenal crisis symptoms
sudden severe pain in lower back, severe vomiting and diarrhoea, dehydration, low blood pressure, loss of consciousness
54
What is cushing's syndrome? What are the symptoms
Hypersecretion of cortisol. red cheeks, moon face, fat pads, thin skin, red striations, high blood pressure, thin arms and legs, pendulous abdomen, poor wound healing
55
Causes of Cushing's disease
pituitary tumor adrenocortical tumors
56
What are the two classes of Cushing's syndrome?
Adrenocorticotrophic (ACTH) dependent; body making too much ACTH due to pituitary or ectopic tumor Adrenocorticotrophic (ACTH) independent; ACTH level too low, Adrenal glands making too much cortisol due to adrenal tumor
57
What drug interactions may cause Cushing's syndrome?
Drugs that inhihibt P450 enzymes as they prolong the action of glucocorticoids e.g. many antidepressants, itraconazole, ritonavir

MP322 (5 decks)

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