physiology- thyroid gland

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What is hyperplasia and hypertrophy?
hyperplasia- the enlargement of a tissue or gland caused by an increase in the reproduction rate of its cells. Hypertrophy is the enlargement of a gland/ tissue from the increase in size of its cells.
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What does hyperplasia and hypertrophy depend on?
genetic contribution, nutrition, and multiple hormones that regulate the linear growth
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what are some examples of these hormones?
GH, IGF-1, IGF-2, insulin, TH, glucocorticoids, androgens and oestrogens
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which of these hormones have been implicated as the major determinants of growth in normal postuterine life
gh, IGF-1
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What does control of body mass depend on?
factors made in adipose, intestine, hypothamaklus+ other tissues that regulate appetite and energy expenditure
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What regulates body mass? which hormones
leptin and ghrelin. Leptin is a hormone, made by fat cells, that decreases your appetite. Ghrelin is a hormone that increases appetite, and also plays a role in body weight.
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Give some features of leptin
Protein made in adipocytes. plasma leptin levels are directly proportional to mass of adipose tissues. It crosses the BBB to modulate specific neurons in the arcuate nucleus of the hypothalamus that control feeding behaviour. Long term CNS feeding be
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Give some features of ghrelin
Promotes appetite- increases food intake when given any physiological doses. synthesised by endocrine cells in the gastric mucosa in response to fasting. acts via the arcuate nucleus of the hypothalamus
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What are the thyroid hormones?
T3-Triiodothyronine, T4- Thyroxine (tetraiodothyronine) + calcitonin- synthesised by C cells parafollicular cells
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How do these hormones act on tissues?
act via nuclear receptors and regulate transcription of cell proteins
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How are the thyroid hormones synthesised?
Production and accumulation of the raw materials (in the case of ICs, a large wafer of doped silicon) Fabrication or synthesis of the hormones on a backbone or scaffold of precursor (etching several ICs on the silicon wafer) Release of the free hor
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What tissues metabolise T4 and T3
non thyroidal tissues - the liver and kidneys
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what are the plasma proteins to which the thyroid hormones (T3 and T4) are bound to during circulation?
Thyroid binding globulin (TBG) albumin and transthyretin (TTR)
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What does a large pool of T4 provide?
a reverse of prohormone available for synthesis of T3
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What are some of the actions of thyroid hormones on target cells?
Makes Na-K pump, gluconeogenetic enzymes, respiratory enzymes, myosin heavy chain, beta- adrenergic receptors
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What do the thyroid hormones do to the basal metabolic rate
They increase it by stimulating both catabolic and anabolic reactions in pathways affecting fats, CHO and proteins
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How do the thyroid hormones affect CHO metabolism
The thyroid hormones increase hepatic gluconeogenic activity by inducing the expression of several key gluconeogenic enzymes
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How do the thyroid hormones affect protein metabolism
they increase protein synthesis . they increase proteolysis in muscle by releasing amino acids to be used for hepatic gluconeogenesis (proteolysis> synthesis)
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What is hyperthyroidism?
overactivity of the thyroid gland, resulting in a rapid heartbeat and an increased rate of metabolism.
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How do thyroid hormones affect lipid metabolism?
they increase degradation of stored triglycerides in adipose tissue and provides glycerol for hepatic gluconeogenesis. FFAs also released to provide fuel for liver. they increase lipogenesis but high T3 levels favour lipolysis and loss of fat stores
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What hypothyroidism
abnormally low activity of the thyroid gland, resulting in retardation of growth and mental development in children and adults.
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When theres a low level of thyroid hormones, how is the basal metabolic rate, carbohydrate metabolism, protein, lipid and thermogenesis affected?
BMR- decreases, gluconeogenesis and glycogenolysis decreases. but normal serum [glucose]. synthesis and proteolysis decreases. lipogenesis, lipolysis decreases. serum [cholesterol] increases, thermogenesis decreases
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When theres a high level of thyroid hormones, how is the basal metabolic rate, carbohydrate metabolism, protein, lipid and thermogenesis affected?
opposite to the low level effects
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what causes cretinism
iodine deficiency or congenital defects in TH synthesis
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what is cretinism
profound mental retardation, short stature, delay in motor development, coarse hair and protuberant abdomen
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Thyroid releasing hormone from the hypothalamus stimulates what to secrete thyroid stimulating hormone?
thyrotrophs.
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what does TSH do
stimulate T4 and T3 synthesis
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what is the cause of graves disease?
abnormal immunoglobulin- TSI
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How does the TSI work
binds to and activates the TSH receptor. leads to increased secretion of T3 and T4 and the thyroid enlarges to form a goiter
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what are some of the symptoms of Hyperthyroidism if left untreated?
sweating and heat intolerance, rapid and more forceful heartbeat. muscle weakness and wasting. changes in hair growth and skin texture. increased metabolic rate with associated weight loss
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what is exophthalmos
forward protrusion of the eyes because TSI stimulates CT in the extra ocular muscles
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Iodine deficiency and autoimmune disorder (Hashimoto thyroiditis) can cause hypothyroidism. what is this immune disorder
production of antithyroid antibodies that block and destroy thyroid function
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what happens if the disease does evolve?
goiter, skin changes peripheral oedema, constipation, headache, joint aches, fatigue and anovulation in females
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What does hyperplasia and hypertrophy depend on?

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genetic contribution, nutrition, and multiple hormones that regulate the linear growth

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what are some examples of these hormones?

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Card 4

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which of these hormones have been implicated as the major determinants of growth in normal postuterine life

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What does control of body mass depend on?

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