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Physiology > Endocrine 3 > Flashcards

Endocrine 3 Flashcards

1
Q

4 factors that influence growth apart form growth hormone

A
  • Genetic determination
  • An adequate diet
  • Freedom from chronic disease and stressful environment
  • Normal levels of growth-influencing hormones
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2
Q

Stressful environment influencing growth

A

Stunted growth from stress induced secretion of cortisol –over a prolonged period of time.
- Cortisol can promote protein breakdown, inhibiting growth of long bones and block the secretion of GH.

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3
Q

Growth influencing hormones role

A

In addition to GH, hormones including thyroid hormone, insulin and the sex hormones play secondary roles in promoting growth

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4
Q

2 major regulators of growth

A
  • Growth hormone

* Somatomedins (IGFs; insulin growth factors)

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5
Q

Other growth influencing hormones x 4

A
  • Oestrogens / Testosterone
  • Insulin
  • Thyroid hormones
  • Calcitonin, PTH and Vitamin D
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6
Q

Other growth FACTORS

A
  • Epidermal Growth Factor
  • Platelet Derived Growth Factor
  • Nerve Growth Factor
  • Fibroblast Growth Factor
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7
Q

Function of Platelet Derived Growth Factor

A

Stimulates fibroblasts and glial cell growth

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8
Q

Function of nerve growth factor

A

Neuronal survival and synaptic out-growth

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9
Q

Function of fibroblast growth factor

A

Stimulates bone cell proliferation and collagen synthesis

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10
Q

What is epidermal growth factor?

A

Polypeptide with mitogenic activity

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11
Q

What is growth hormone also called?

A

Somatotropin

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12
Q

Where is GH encoded?

A

On chromosome 17

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13
Q

Mol wt of GH

A

20kDa

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14
Q

GH - what peptide?

A

Peptide hormone 191 amino acid

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15
Q

Release of GH

A
  • not continuous

* different factors responsible for growth at different periods

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16
Q

Fetal growth (promoted, GH role)

A
  • promoted by placenta hormones

* GH plays no role in fetal growth

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17
Q

When does the postnatal growth spurt occur?

A

First two years of life

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18
Q

Hormones in puberty growth spurt

A
  • Male: Androgens (testes) promote growth

* Female: Androgens (adrenal glands, less potent) promote growth

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19
Q

2 growth periods of rapid growth in children

A

A postnatal growth spurt up to the age of 2 and a pubertal growth spurt during adolescence

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20
Q

Puberty age in girls

A

11

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21
Q

Puberty age in boys

A

13

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22
Q

What hormones promotes sharp increase in height in boys

A

Testosterone

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23
Q

What is most likely involved in female growth spurt?

A

Androgens from the adrenal cortex

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24
Q

What do both testosterone and oestrogen act on and why?

A

On bone to halt its further growth so that full height is attained at the end of adolescence.

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25
Q

Type of release in GH release

A

Pulsed release

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26
Q

GH pulsed release

A

─ released from anterior pituitary in several bursts
─ high morning before awakening, low in day
─ secretion stimulated during deep sleep
─ rhythm linked to sleep-wake not light/dark
─ surges in first 2 hr sleep at night

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27
Q

Number / magnitude of GH release in age

A
  • high in puberty
  • low in adults
  • absent at 50yr+
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28
Q

Age-related decrease in GH release causes

A
  • change in muscle:fat ratio
  • decreased bone density
  • GH sold as “anti-ageing” therapy? (but may actually speed ageing)……..
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29
Q

What are GHRH (growth hormone releasing hormone) and somatostatin produced by?

A

Hypothalamic neurons

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30
Q

GHRP receptor type

A

a 7 transmembrane domain G-protein coupled receptor

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31
Q

What does GHRH stimulate?

A

GH synthesis and secretion

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32
Q

What is GH initiated by?

A

By bursting secretion of GHRH

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33
Q

What is GH terminated by?

A

Somatostatin

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34
Q

What does injection of GH into animals cause? x 6

A
  • increases glucose levels in blood
  • promotes protein synthesis
  • promotes lipolysis in adipocytes
  • promotes bone growth
  • results in erythropoesis
  • has anti-insulin activity
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35
Q

Long term metabolic effects of GH x 4

A 
Carbohydrates
- increases glucose levels in blood
Proteins Synthesis
- increases tissue amino acid uptake
Lipids (Lipolysis)
- increases free fatty acids in blood
Stimulates Growth
- stimulates IGF production
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36
Q

What does GH release?

A

IGF-1

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37
Q

What does GH stimulate? x 3

A
  • Liver production of somatomedins (insulin-like growth factor; IGF-1)
    – Acts on bone & soft tissues to promote growth
    – Protein synthesis, cell division (of chondrocytes), lengthening, thickening of bones
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38
Q

Metabolic effects of GH

A

– increases fatty acid levels in blood (by breakdown of fat)

– increases blood glucose levels (by decrease of glucose uptake by muscles)

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39
Q

Hypothalamus diagram for GH

A
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40
Q

What does GH mediate actions via?

A

IGFs

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41
Q

Why does GH stimulate the liver?

A

To produce IGFs

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42
Q

What are IGFs (insulin-like growth factors) structurally related to?

A

Insulin

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43
Q

What does IGF stimulate?

A
  • Bone and soft tissue growth
  • Hyperplasia: cell proliferation
  • Hypertrophy: increasing the size of cells
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44
Q

What does IGF prevent?

A

Apoptosis

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45
Q

Mice genetically lacking GH are …

A

Dwarfed

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46
Q

x 3 GH diseases

A
  • Pituitary Gigantism
  • Acromegaly
  • Dwarfism
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47
Q

Pituitary giantism cause

A

GH excess caused by tumour cells of anterior pituitary

48
Q

Pituitary giantism name in adults

A

Acromegaly

49
Q

What causes acromegaly

A

GH hypersecretion after adolescence

50
Q

What cause GH hypersecretion in acromegaly?

A

Benign tumors (adenomas) in pituitary gland

51
Q

Feature of acromegaly x 5

A 
– thickening of bones
– coarsened facial features
– soft tissue swelling (hands and feet)
– heart failure
– vision loss (compressed optic chiasm)
52
Q

Medication reduce GH secretion/tumor x 3

A

– Bromocriptine (DA receptor agonist)
– somatostatin, to stop GH production
– GH receptor antagonists are emerging

53
Q

4 types of dwarfism

A
  • GH deficiency
  • Hereditary
  • Laron dwarf
  • African Pygmy
54
Q

GH deficiency dwarfism

A
  • low GH

* treated by replacing with GH

55
Q

Hereditary dwarfism cause

A

Low GHRH

56
Q

Laron dwarf cause

A

Defective GH receptor

57
Q

African pygmy cause

A

Defective IGF1 receptor

58
Q

Feedback loop of GH

A
59
Q

NB - Metabolic effects of GH not related to growth

A

Increases fatty acid levels in the blood by enhancing breakdown of triglyceride fat stored in adipose tissue.
Increases blood glucose by decreasing glucose uptake by muscles and increasing glucose output by the liver– muscle use mobilised fatty acids as fuel instead of glucose.

60
Q

Overall metabolic effect of GH

A

mobilise fat stores as a major energy substrate while conserving glucose for glucose dependent tissues such as brain.

61
Q

Hypothyroid children growth affect

A

Growth severely stunted.

62
Q

Hypersecretion growth affect

A

Does not affect growth.

63
Q

Insulin function

A

Growth promoter.

Promotes protein synthesis.

64
Q

Insulin deficiency growth consequence

A

Blocks growth

65
Q

Hyperinsulinism

A

Spurs excessive growth

66
Q

Thyroid hormone permissive role

A

Permissive role in skeletal growth; the actions of GH only manifest when sufficient TH is present.

67
Q

Thyroid hormone need

A

Necessary for growth BUT not directly responsible for promoting growth

68
Q

Other hormones responsible for growth

A

Androgens

Oestrogens

69
Q

Androgens function

A
  • Pubertal growth spurt, stimulate protein synthesis in many organs.
  • Stimulate linear growth
  • Promote weight gain
  • Increase muscle mass
70
Q

Whats the most potent androgen?

A

Testosterone

71
Q

Testosterone function

A

Promotes a sharp increase in height in adolescent boys.

72
Q

In the absence of GH, what is the effect of androgens?

A

Virtually no effect on body growth

73
Q

Oestrogens growth function

A

Thought to contribute to the pubertal growth spurt in females but its exact role is uncertain.

74
Q

Location of thyroid gland

A

Located on the front of upper part of trachea

75
Q

What does the thyroid gland develop from?

A

Epithelial outgrowth of tongue

76
Q

What does the thyroid gland develop from?

A

Epithelial outgrowth of tongue

77
Q

Major secretory cells of thyroid gland

A

Follicular cells, arranged in hollow spheres – functional unit is a follicle

78
Q

Follicles appearance and structure

A

Appear as rings consisting of a single layer of follicular cells enclosing an inner lumen filled with colloid

79
Q

Colloid function

A

Serves as an extracellular storage site for TH.

80
Q

Name a major constituent of colloid

A

Large glycoprotein molecule known as thyroglobulin (Tg) – incorporated into TH during their synthesis.

81
Q

x 3 Types of thyroid hormones

A
  • T3 (Triiodotyronine) - in follicles
  • T4 (Thyroxine) - in follicles
  • Calcitonin by C cells
82
Q

Calcitonin role

A

Role in Calcium metabolism not related to T3/T4

83
Q

Function of T3 and T4

A
  • Accelerate metabolism

* Increase carbohydrate, fat and protein turnover

84
Q

T3 and T4, what type of hormone base

A

Tyrosine-based hormones

85
Q

T3 and T4 structure

A

T3 has 3 iodine atoms, T4 contains 4

86
Q

T3 and T4 compare effectiveness

A

T3 more effective, but T4 more abundant

87
Q

What are levels of T3 and T4 controlled by?

A

Anterior pituitary TSH

88
Q

Transport of T3, T4

A

In blood, bound to thyroxine-binding globulin (TBG)

89
Q

T3 and T4 produced

A

Made by follicular cells when iodide available

90
Q

Hoe is iodide absorbed?

A

Absorbed from blood to thyroid follicles

91
Q

Synthesis, Storage and secretion of TH

A
92
Q

x 6 Effects of thyroid glands

A
  • Main determinant of basal metabolic rate
  • Influences synthesis and degradation of carbohydrate, fat and protein
  • Increases target cell responsiveness to catecholamines
  • Increases heart rate and force of contraction
  • Essential for normal growth
  • Plays crucial role in normal development of the nervous system
93
Q

Feedback loops of thyroid hormone

A
94
Q

Low iodine uptake disease

A

Goiter

95
Q

Goiter disease

A

dietary iodide insufficiency

  • no T3/T4 made
  • thyroid cell proliferation
  • iodide uptake increases
  • normal human thyroid gland of 25g may grow to 250 g during goiter
96
Q

Thyroid autoimmune disease

A

Hashimoto’s

97
Q

What happens in hashimotos?

A

Autoantibodies destroy thyroid follicular cells

98
Q

Hypothyroidism infant disease

A

Cretinism

99
Q

Cretinism ‘symptoms’

A
  • stunted growth
  • lack of bone formation
  • skeletal abnormalities
  • severe mental retardation
  • Protruding tongue
100
Q

Hypothyroidism cause

A
  • Primary failure of the thyroid gland itself
    Secondary to a deficit of TRH, TSH or both
  • Inadequate dietary supply of iodide
101
Q

Hypothyroidism in older children adult disease

A

Myxedema

102
Q

Clinical features of myxedema

A
  • Generalised fatigue
  • Mental slugglishness
  • Slow speech
  • Cold intolerance
  • Overweight
  • Shortness of breath
  • Constipation
  • Decreased sweating
  • Cool and pale skin
  • Generalized edema
  • Enlargement of tongue
  • Deepened voice
103
Q

Hyperthyroidism symtoms

A
  • high metabolic rate
  • protruding eyes
  • hyperactivity, insomnia
  • heat sensitivity, weight loss, always hot
104
Q

Hyperthyroidism disease

A

Grave’s disease

105
Q

What is Grave’s disease

A

Autoimmune (TSH mimicked by autoantibodies – also known as thyroid stimulating immunoglobulin (TSI))

106
Q

Grave’s disease treatments

A

– Beta blockers help some symptoms
– Anti-thyroid medications
– Radioactive iodine treatment destroys overactive thyroid cells
– Surgery thyroidectomy

107
Q

Cause of hypothyroidism

A
  • Primary failure of the thyroid gland
  • Secondary to hypothalamic or anterior pituitary failure
  • Lack of dietary iodine
108
Q

Plasma concentrations of relevant hormones in primary failure of the thyroid gland

A

↓T3 and T4, ↑ TSH

109
Q

Plasma concentrations of relevant hormones in secondary to hypothalamic or anterior pituitary failure

A

↓T3 and T4, ↑ TRH and/or ↓ TSH

110
Q

Hypothyroidism - Plasma concentrations of relevant hormones in lack of dietary iodine

A

↓T3 and T4, ↑ TSH

111
Q

x 3 Causes of hyperthyroidism

A
  • Abnormal presence of thyroid-stimulating immunoglobulin (TSI) (Grave’s disease)
  • Secondary to excess hypothalamic or anterior pituitary secretion
  • Hypersecreting thyroid tumor
112
Q

Hyperthyroidism - Plasma concentrations of relevant hormones in abnormal presence of thyroid-stimulating immunoglobulin (TSI) (Grave’s disease)

A

↑ T3 and T4,↓ TSH

113
Q

Hyperthyroidism - Plasma concentrations of relevant hormones in secondary to excess hypothalamic or anterior pituitary secretion

A

↑ T3 and T4, ↑ TRH and/ or TSH

114
Q

Hyperthyroidism - Plasma concentrations of relevant hormones in hypersecreting thyroid tumour

A

↑ T3 and T4,↓ TSH

115
Q

What disfunction cause of hyper and hypothyroidism doesn’t have goiter?

A
  • Hypersecreting thyroid tumour

- Secondary to hypothalamic or anterior pituitary failure

Physiology (28 decks)

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