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SUGER > Endocrinology > Flashcards

Endocrinology Flashcards

1
Q

Hormone

A

A substance secreted directly into the blood by specialised cells
Present in only minute concentrations in the blood and bind specific receptors in target cells to influence cellular reactions

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2
Q

Endocrine organs

A

Heart
Liver
Fat
Kidney
Skin
Intestines

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3
Q

Endocrine glands

A

Hypothalamus
Pituitary
Thyroid
Parathyroid
Adrenals
Pancreas
Ovary/testes

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4
Q

Endocrine glands

A

Hypothalamus
Pituitary
Thyroid
Parathyroids
Adrenals
Pancreas
Ovary/testes

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5
Q

3 hormone structures

A

Steroid
Peptide
Thyroid hormones

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6
Q

What are all steroid hormones synthesised from

A

Cholesterol

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7
Q

What are Catecholamines synthesised from

A

Tyrosine

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8
Q

Storage of peptide hormones

A

Day

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9
Q

Storage of steroid hormones

A

Min-hour

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10
Q

What is important for the production of thyroid hormone

A

Iodine

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11
Q

Substrates for thyroid hormone

A

Thyroglobulin
Tyrosine

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12
Q

Storage of thyroid hormones

A

Weeks

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13
Q

Storage of Catecholamines hormones

A

Day

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14
Q

Secretion of peptide hormones

A

Exocytosis

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15
Q

Secretion of steroid hormones

A

Diffusion

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16
Q

Secretion of thyroid hormones

A

Proteolysis

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17
Q

Secretion of Catecholamines hormones

A

Exocytosis

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18
Q

Binding protein required for peptide hormones?

A

Some

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19
Q

Binding protein required for steroid hormones?

A

All

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20
Q

Binding protein required for thyroid hormones?

A

Yes

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21
Q

Binding protein required for Catecholamines hormones?

A

No

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22
Q

Time to action of peptide hormones

A

Min-hour

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23
Q

Time to action of steroid hormones

A

Hour-day

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24
Q

Time to action of thyroid hormones

A

Day

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25
Q

Time to action of Catecholamines hormones

A

Seconds

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26
Q

Half life of peptide hormones

A

Min-hour

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27
Q

Half life of steroid hormones

A

Hours

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28
Q

Half life of thyroid hormones

A

Days

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29
Q

Half life of Catecholamines hormones

A

Sec-min

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30
Q

How do hormones exert their effect

A

Cell surface receptors
Intracellular receptors

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31
Q

Cell surface receptors

A

G protein coupling

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32
Q

Basic actions of thyroid hormone

A

Basal metabolic rate
Growth

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33
Q

Basic actions of parathyroid

A

Ca2+ regulation

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34
Q

Basic actions of cortisol

A

Glucose regulation
Inflammation

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35
Q

Basic actions of aldosterone

A

Blood pressure
Na_ regulation

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36
Q

Basic actions of Catecholamines

A

Blood pressure
Stress

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37
Q

Basic actions of oestradiol

A

Menstruation
Femininity

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38
Q

Basic actions of testosterone

A

Sexual function
Masculinity

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39
Q

Basic actions of insulin

A

Glucose regulation

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40
Q

Basic actions of ANP

A

Na+ regulation

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41
Q

Basic actions of vitamin D

A

Ca2+ regulation

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42
Q

How to measure hormone concentrations

A

Bioassays
Immunoassays
Mass spectrometry

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43
Q

Anterior pituitary hormone

A

ACTH
TSH
GH
LH/FSH
PRL

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44
Q

Basic actions of ACTH

A

Regulation of adrenal cortex

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45
Q

Basic actions of TSH

A

Thyroid hormone regulation

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46
Q

Basic actions of GH

A

Growth
Metabolism

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47
Q

Basic actions of LH/FSH

A

Reproductive control

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48
Q

Basic actions of PRL

A

Breast milk production

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49
Q

Posterior pituitary hormones

A

ADH
Oxytocin

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50
Q

Basic actions of ADH

A

Water regulation

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51
Q

Basic actions of oxytocin

A

Breast milk expression

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52
Q

Available treatment for thyrotoxicosis

A

Destruction of thyroid tissue using radioiodine (131I)
Antithyroid drugs to block hormone synthesis
Partial surgical ablation of thyroid

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53
Q

Drugs used to treat functioning pituitary tumours

A

Somatostatin analogues
Dopamine agonists
GH receptor antagonists

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54
Q

How to treat under active glands

A

Hormone replacement therapy

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55
Q

Location of adrenal gland

A

Sit on supramedial aspect of kidneys

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56
Q

Are the adrenal glands Intraperitoneal or retroperitoneal

A

Retroperitoneal

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57
Q

Blood supply to adrenal glands

A

Superior, middle and inferior adrenal arteries

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58
Q

What is the superior adrenal artery a branch of

A

Inferior phrenic

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59
Q

What is the middle adrenal artery a branch of

A

Abdominal aorta

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60
Q

What is the inferior adrenal artery a branch of

A

Renal artery

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61
Q

What does the right adrenal gland drain into

A

Directly into IVC

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62
Q

What does the left adrenal gland drain into

A

Left renal vein and then IVC

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63
Q

Which nerve innervates the adrenal gland

A

Splanchnic nerve

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64
Q

Which type of hormones are produced in the adrenal medulla

A

Catecholamines

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65
Q

Which hormones are produced in the adrenal medulla

A

Adrenaline - 80%
Noradrenaline- 20%

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66
Q

What is Catecholamines synthesis dependent on

A

Cortisol levels

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67
Q

What system is the adrenal medulla part of

A

Autonomic nervous system
- specialised ganglia used ACh s a neurotransmitter

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68
Q

Noradrenaline receptors

A

Alpha

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69
Q

Adrenaline receptors

A

Beta

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70
Q

Effects of hormones released by adrenal medulla

A

Gluconeogenesis
Lipolysis
Tachycardia
Redistribution of circulatory volume

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71
Q

Which type of hormone is produced in the Zona glomerulosa of adrenal gland

A

Mineralocorticoids

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72
Q

Which hormone does the zona glomerulosa of the adrenal gland

A

Aldosterone

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73
Q

What triggers secretion of aldosterone

A

Renin

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74
Q

Cortisol can act on,,,…..

A

Mineralcorticoid receptors

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75
Q

Pre-receptor regulation of cortisol is by

A

11B-HSD2

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76
Q

Effects of hormones released by zona glomerulosa of adrenal gland

A

Salt balance in the kidneys, colon, pancreas, salivary glands and sweat glands
- in DCT increases ENaC expression apically and Na/K ATPase expression basolaterally

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77
Q

Which type of hormones does the zona fasciculata of the adrenal gland produce

A

Cortisol
Corticosterone

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78
Q

What does the hypothalamus release - cortisol

A

Corticotropin releasing hormone CRH

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79
Q

Action of corticotropin releasing hormone

A

Acts on anterior pituitary to stimulate ACTH release

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80
Q

Action of ACTH

A

Binds to GPCRs (Gs subunits) in zona fasciculata of the adrenal gland
Protein kinase A stimulates synthesis of cholesterol
Cholesterol converted to pregnenolone in mitochondria
Further processing in endoplasmic reticulum
Conversion to cortisol in mitochondria

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81
Q

Precursors of cortisol

A

Cholesterol
Pregnenolone
Cortisol

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82
Q

Cortisol in blood

A

90% bound to corticosteroid-binding globulin
5% bound to albumin
5% free

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83
Q

Stress and corticosteroid-binding globulin

A

Stress promotes the release from CBG which means more is free and can be utilised

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84
Q

Effects of cortisol

A

Increased energy mobilisation
Increased amino acid generation - muscle catabolism
Vascular tone- promotes shunt to periphery
Salt and water balance
Immune suppression
Inhibits growth and reproduction

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85
Q

Permissive effect

A

Allows another action to take place eg vasoconstriction via Catecholamines

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86
Q

Diurnal rhythm of cortisol

A

High levels in morning and early afternoon

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87
Q

Negative feedback and cortisol

A

Cortisol acts on hypothalamus and pituitary

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88
Q

Which type of hormones are produced in the zona reticularis of adrenal gland

A

Androgens

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89
Q

Most abundant androgen produced by zona reticularis of adrenal gland

A

DHEA

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90
Q

Most potent androgen produced by the zona reticularis of adrenal gland

A

Testosterone

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91
Q

Androgens produced by the zona reticularis of adrenal gland

A

DHEA
Testosterone
Androstenedione

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92
Q

What regulates androgen release from zona reticularis of adrenal gland

A

ACTH

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93
Q

Androstenedione in women

A

Converted to testosterone in peripheral tissues

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94
Q

3 glands involved in cortisol release

A

Hypothalamus
Pituitary
Adrenal gland

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95
Q

3 hormones involved in cortisol release

A

CRH
ACTH
Cortisol

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96
Q

What can trigger release of CRH from hypothalamus (eventually cortisol)

A

Stress
Cytokines
Diurnal rhythm

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97
Q

Location of thyroid gland

A

Anterior neck between C5 and T1

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98
Q

Structure of thyroid gland

A

2 lobes connected by isthmus

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99
Q

Arterial supply to thyroid gland

A

Superior and inferior thyroid glands

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100
Q

What is the superior thyroid artery a branch of

A

1st branch of external carotid artery

101
Q

What is the inferior thyroid artery a branch of

A

Subclavian artery

102
Q

What does the superior thyroid artery supply

A

Superior and anterior portions

103
Q

What does the inferior thyroid artery supply

A

Posterior and inferior portions

104
Q

What drains the thyroid gland

A

Middle and inferior thyroid veins

105
Q

Size and weight of pituitary gland

A

Pea-sized
Weighs 0.5g

106
Q

What does the pituitary gland respond to

A

Hypothalamus

107
Q

Blood supply to anterior pituitary gland

A

No arterial blood supply
Receives blood through portal venous circulation from hypothalamus

108
Q

Which hormones released from the anterior pituitary are glycoproteins

A

TSH
FSH
LH

109
Q

Which hormones released from the anterior pituitary are polypeptides

A

ACTH
GH
Prolactin

110
Q

Name of portal system between hypothalamus and pituitary gland

A

Hypothalamic-hypophyseal portal system

111
Q

Which hormone released by the hypothalamus stimulates the release of TSH

A

TRH -thyrotopin releasing hormine

112
Q

Which hormone released by the hypothalamus stimulates the release of ACTH

A

Corticotropin releasing hormone

113
Q

Which hormone released by the hypothalamus stimulates the release of FSH

A

GnRH

114
Q

Which hormone released by the hypothalamus stimulates the release of LH

A

GnRH

115
Q

Which hormone released by the hypothalamus stimulates the release of growth hormone

A

GH releasing hormone

116
Q

What inhibits the release of prolactin

A

Dopamine

117
Q

What inhibits the release of growth hormone

A

Somatostatin

118
Q

What stimulates growth hormone

A

Low glucose
Exercise
Sleep

119
Q

What suppresses growth hormone

A

Hyperglycaemia

120
Q

What mediates the effects of growth hormone

A

GH and IGF1

121
Q

Actions of growth hormone

A

Linear growth in children
Acquisition of bone mass
Stimulates - protein synthesis, lipolysis, glucose metabolism
Regulation of body composition
Psychological well-being

122
Q

What regulated thyroid hormone levels

A

Negative feedback loop between TSH and thyroxine

123
Q

Where is prolactin synthesised

A

Lactotrophs

124
Q

Prolactin function

A

Levels increase during pregnancy and breast feeding as important for lactation
Inhibits gonadal activity through central suppression of GnRH

125
Q

Physiological hyperprolactaemia

A

Physical or psychological stress
Post seizure
Greater in women
Rarely exceeds 850-1000 mU/L
PRL has circadian rhythm with peak during sleep

126
Q

Embryology of pituitary gland

A

Anterior and posterior glands develop from different tissues before joining together

127
Q

Embryology of anterior pituitary

A

Protrusion of ectoderm from Rathke’s pouch grows upwards to form anterior pituitary (adenohypophysis)

128
Q

Embryology of posterior pituitary

A

Neuronal (neurohyophysis)
Extension of neural components of hypothalamus

129
Q

What causes the secretion of hormone of hypophysiotropic hormones

A

Generation of AP in neurons of hypothalamus

130
Q

What do all pituitary and hypothalamic hormones act on

A

G-protein coupled receptors (GPCRs)

131
Q

Long-looped negative feedback

A

Hormone secreted by 3rd endocrine gland exerts negative feedback

132
Q

In which cells is FSH/LH produced

A

Gonadotrophs

133
Q

Function of FSH

A

Stimulates germ cell development and release of hormones

134
Q

In which cells is ACTH produced

A

Corticotrophs

135
Q

In which cells is TSH produced

A

Thyrotrophs

136
Q

Function of TSH

A

Stimulates thyroid to secrete T3 and T4– increases metabolism

137
Q

Main hormone involved in negative feedback of HPG axis

A

Inhibin (and progesterone/ oestrogen or testosterone)

138
Q

In which cells is prolactin produced

A

Lactotrophs

139
Q

In which cells is GH produced

A

Somatotrophs

140
Q

What nerves innervate the thyroid gland

A

Sympathetic trunk

141
Q

T4

A

Thyroxine (4 iodine)

142
Q

T3

A

Triiodothronine (3 iodine)

143
Q

What converts T4 to T3

A

Deiodinase enzymes

144
Q

What 2 iodine-containing molecules does the thyroid gland produce

A

T4- thyroxine
T3 - triiodothronine

145
Q

Synthesis of thyroid hormone

A

TSH binds to TSH receptors
Iodide actively co-transported across basolateral membrane via NIS (Na/I symporter)
Iodide then diffuses to apical membrane and transported into colloid
Colloid contains thyroglobulin which binds to the oxidised iodide (iodine) via thyroid peroxidase
Tyrosine bind to 1 or 2 iodine molecules resulting in monoiodotyrosine and diiodotyrosine
When thyroid stimulates T1 and T2 are cleaved and joined to create T3 or T4
Proteolysis of thyroglobulin released T3 and T4

146
Q

Which form of thyroid hormone is biologically active

A

T3

147
Q

Is T4 or T3 more abundant

A

T4

148
Q

Where is thyroglobulin stored

A

Colloid - protein-rich material in follicles

149
Q

What catalyses reaction between iodine and thyroglobulin

A

Thyroid peroxidase

150
Q

How is iodide actively transported across basolateral membrane

A

Na/I symporter

151
Q

Function of TSH

A

Acts on thyroid gland to secrete T3 and T4
Increased protein synthesis in follicular cells
Increased DNA replication and cell division
Increases quantity of rough ER

152
Q

How is T4 converted to T3

A

Mono-deiodination catalysed by deiodinase enzymes

153
Q

When does the thyroid gland begin to develop

A

Weeks 3-4

154
Q

Embryology of thyroid gland

A

At weeks 3-4 , glands appear as an epithelial proliferation at base of pharynx
Glands then migrate down the thyroglossal duct to below larynx

155
Q

When do the thyroid glands begin to produce thyroxine

A

18-20 weeks

156
Q

Actions of thyroid hormone

A

Increases metabolic rate
Brain maturation

157
Q

How does T3 increase metabolic rate

A

Stimulates carbohydrate absorption from small intestine and increases fatty acid release from adipocytes
- energy supports activity of Na/K ATPases , increasing heart production—> temperature homeostasis

158
Q

How is T3 involved in temperature homeostasis

A

Increasing metabolic rate

159
Q

T3 and growth and development

A

Required for normal production of growth hormone
Involved in nervous system development

160
Q

How is T3 involved in nervous system development

A

Formation of axon terminals
Production of synapses
Growth of dendrites and dendritic extensions
Formation of myelin

161
Q

Location of parathyroid glands

A

Posterior aspect of lateral lobes of thyroid

162
Q

Number of parathyroid glands

A

2 superior
2 inferior

163
Q

Arterial supply to parathyroid glands

A

Inferior thyroid artery- from subclavian artery

164
Q

Drainage of parathyroid glands

A

Into thyroid plexus

165
Q

Innervation of parathyroid gland

A

Sympathetic trunk- only vasomotor

166
Q

Function of parathyroid gland

A

Regulates calcium and phosphate levels

167
Q

Function of parathyroid hormone

A

Increase calcium reabsorption in DCT
increases intestinal calcium absorption (via activation of vitamin D)- duodenum and Jejunum
Increases calcium release from bone (stimulates osteoclast activity)
Decreases phosphate reabsorption
Bind to GPCRs

168
Q

What inhibits PTH transcription

A

1,25D3

169
Q

What inhibits PTH translation

A

Increased serum calcium

170
Q

What stimulates secretion of parathyroid hormone

A

Low calcium
High phosphate

171
Q

How does PTH increase instestinak calcium absorption

A

Activation of vitamin D

172
Q

Where does PTH increase intestinal calcium absorption

A

Duodenum
Jejunum

173
Q

How does PTH increase calcium release from bone

A

Stimulates osteoclasts actiivty

174
Q

Hyperparathyroidism

A

Raised serum PTH

175
Q

Primary hyperparathyroidism

A

Parathyroid tumour
Causes hypercalcaemia and low serum phosphate
Loss of negative feedback from hypercalcaemia
Treatment is surgery

176
Q

Secondary hyperparathyroidism

A

Renal disease
Increased phosphate and decreased activation of vitamin D
Treat with phosphate binders or vitamin D analogues

177
Q

Tertiary hyperparathyroidism

A

Long-standing secondary hyperparathyroidism leads to irreversible parathyroid hyperplasia
Usually seen when renal disease is corrected, transplantation
Treatment is surgery

178
Q

Parathyroid hormone response to hypercalcaemia

A

Decreases PTH secretion

179
Q

Decrease PTH secretion in response to hypercalcaemia

A

Increases calcitonin —> Decreases bone resorption
Decrease urinary phosphate and 1,25D3 production
Increase urinary calcium
Decrease calcium and phosphate absorption

Decreases serum calcium

180
Q

Parathyroid hormone response to hypocalcaemia

A

Increases PTH secretion

181
Q

Increased PTH secretion in response to hypocalcaemia

A

Increases bone resorption
Increases urinary phosphate
Increases 1,25D3 production
Decreases urinary calcium
Increases calcium and phosphate absorption

Increases serum calcium

182
Q

1,25D3

A

Affects absorption of calcium and phosphate in small intestine

183
Q

Where is ADH synthesised in posterior pituitary

A

Supraoptic nucleus

184
Q

What causes release of ADH

A

Increased osmotic pressure in blood
Decreased blood volume
Trauma/stress
Increased PCO2
Decreased PO2

185
Q

Effects of ADH

A

Increased AQP2 expression in cortical collecting duct cells
Vasoconstriction of smooth muscle cells around blood vessels

186
Q

Where is oxytocin synthesised in posterior pituitary

A

Paraventricular nucleus

187
Q

What stimulates release of oxytocin

A

Nipple stimukation

188
Q

Effects of oxytocin

A

Constriction of muscles of breast to promote milk ejection
Uterine smooth muscle contractions
Promotion of labour

189
Q

What type of hormone does the posterior pituitary produce

A

Peptide

190
Q

How are the hypothalamus and posterior pituitary connected

A

Via neurons through the infundibulum- hypophyseal system

191
Q

Exocytosis from posterior pituitary is via…

A

Herring bodies

192
Q

What inhibits ADH release

A

Caffeine
Alcohol

193
Q

What stimulates ADH response

A

High osmolality
Low blood volume
Nausea
Vomiting
Stress
Exercise

194
Q

ADH V1a receptors location

A

Vascular smooth muscle
Platelets
Hepatocytes
Myometrium

195
Q

ADH V1a receptors function

A

Vasoconstriction, myocardial hypertrophy
Platelet aggregation
Glycogenolysis
Uterine contraction

196
Q

ADH V1b receptors location

A

Anterior pituitary

197
Q

ADH V1b receptors function

A

ACTH release

198
Q

ADH V2 receptors location

A

Basolateral membrane collecting tubule

199
Q

ADH V2 receptors function

A

Insertion of AQP2 water channels into apical membrane
Induction of AQP2 synthesis

200
Q

Types of ADH receptors

A

V1a
V1b
V2

201
Q

Osmolality

A

Concentration of particles per kilo of fluid

202
Q

What molecules affect osmolality

A

Sodium, potassium, chloride, bicarbonate, urea and glucose
Alcohol , methanol, polyethylene glycol or mannitol

203
Q

Normal osmolality

A

282-295 mOsmol/kg

204
Q

When calculating plasma osmolality why do you x2 Na+

A

Accounts for anions associated with Na+

205
Q

Why is there a 0-10 mOsmol/kg gap between measures and calculated plasma osmolality

A

Higher usually due to alcohol

206
Q

Osmotic threshold for ADH release and pregnancy

A

Decreased
Thirst also decreased

207
Q

What causes plasma ADH concentrations to increase

A

Age
Thirst blunting
Decreased renal concentrating ability
Decreased fluid intake

208
Q

Polyuria

A

Large volumes of urine

209
Q

Polydypsia

A

Large volumes of drinking water

210
Q

Causes of ADH deficiency

A

Destruction of hypothalamus
Interruption of connection of hypothalamus to pituitary

211
Q

What is the precursor for all adrenal steriodogenesis

A

Cholesterol

212
Q

Corticosteroids structure

A

Cyclopentanoperhydrophenanthrene structure
3 cyclohexane rings
Single cyclopentane ring

213
Q

Mechanism of corticosteroids

A

Lipid soluble
Bind to specific intracellular receptors
Alter gene transcription directly or indirectly

214
Q

Classification of steroids

A

Pregnane derivatives - 21 carbons, progesterone and corticoids
Androstane derivatives- 19 carbons, androgens
Estrane derivatives - 18 carbons , oestrogens

215
Q

What stimulates corticosteroid synthesis

A

ACTH

216
Q

What can cortisol bind to

A

Mineralcorticoid receptor and glucocorticoid receptors
- excess binding to MR = Cushing disease

217
Q

Actions of glucocorticoids

A

Increase glucose mobilisation - gluconeogenesis, increased lipolysis
Maintenance of circulation- vascular tone, salt and water balance
Immunomodulation- dampen immune response

218
Q

Transport of glucocorticoids

A

90% bound to corticosteroid-binding globulin CBG
5% bound to albumin 5% free

219
Q

What regulates glucocorticoid synthesis

A

ACTH (and CRH) action
Diurnal rhythm
Stress
Illness

220
Q

How does adenocorticotropic hormone regulate glucocorticoid synthesis

A

Acutely stimulates cortisol release

Stimulates corticosteroid synthesis (and capacity)

CRH stimulates ACTH release

Negative feedback of cortisol on CRH and ACTH production

221
Q

What type of glucocorticoid is bioavaible

A

‘Free’

222
Q

Action of Mineralcorticoids

A

Effect on pancreas, sweat glands, salivary glands, colon and kidney to increase sodium resorption
Myocardial collagen production
Role in cardiac fibrosis/remodelling

223
Q

What is production of adrenal androgens regulated

A

ACTH

224
Q

What is the main source of androgens in women

A

Adrenal glands

225
Q

Main androgens produced by adrenal androgens

A

Dehydroepiandrosterone (DHEA)
Androstenedione

226
Q

What is normal Catecholamines synthesis dependent on

A

High local cortisol levels - permissive effect

227
Q

Stress

A

Sum of the bodies responses to adverse stimuli
I.e.
infection
Trauma
Haemorrhage
Medical illness
Psychological
Exercise/exhaustion

228
Q

What is the neurotransmitter in the adrenal medulla

A

ACh

229
Q

Thyroid hormone synthesis

A

TSH binds to TSHR on basolateral membrane
I- uptake by Na/I symporter
Iodisation of thyroglobulin tyrosyl residues by thyroperoxidase
Coupling of iodotyrosyl residues by thyroperoxidase
Export of mature thyroglobulin to colloid where it is stored

230
Q

Which enzyme binds iodine to tyrosine residues in thyroglobulin molecules to form MIT + DIT

A

Thyroperoxidase

231
Q

Function of thyroperoxidase

A

binds iodine to tyrosine residues in thyroglobulin molecules to form MIT + DIT
MIT + DIT = T3
DIT + DIT =T4

232
Q

Hyperthyroidism

A

Low Serum TSH
High Serum free T4
High Serum free T3

233
Q

Hypothyroidism

A

High Serum TSH
Low Serum free T4
Low Serum free T3

234
Q

Actions of parathyroid hormone

A

Increases calcium reabsorption in renal distal tubule
Increases intestinal calcium absorption (via activation of vitamin D)
Increases calcium release from bone (stimulates osteoclast activity)

Decrease phosphate reabsorption

235
Q

Endocrine control of extracellular calcium homeostasis

A

Parathyroid hormone
Vitamin D
Calcitonin, FGF23

236
Q

Bone and control of bone homeostasis

A

Mineral phase (calcium/phosphate)
Protein phase (collagen and non-collagenous proteins)
Bone cells bone ‘turnover’ and remodelling units

237
Q

How is calcium in the blood

A

50% of serum calcium ‘free’ (ionised)
50% bound to albumin

238
Q

Amount of serum calcium

A

2.1-2.6 mM

239
Q

Structure of parathyroid hormone

A

84 amino acid peptide but biological activity in first 34 amino acids (PTH 1-34), half-life 8 mins
Cleaved to smaller peptides
Assayed by two site assay (to avoid detecting fragments)
Still detects some inactive fragments e.g. in renal failure

240
Q

Normal adult reference range of parathyroid hormone

A

1.6 - 6.9 pmol/L

241
Q

Mechanism of parathyroid hormone activation

A

Binds to G protein coupled receptors mainly in kidneys and osteoblasts

242
Q

Action of parathyroid hormone in kidney

A

PTH increases distal tubular reabsorption of calcium
(+ inhibition of PO4 reabsorption)
PTH also stimulates production of the active form of vitamin D, 1,25(OH)2D

243
Q

Action of parathyroid hormone in bone

A

Enhances bone resorption by stimulating osteoclasts

244
Q

What inhibits parathyroid hormone transcription

A

1,25D3

245
Q

What inhibits parathyroid translation

A

Increased serum calcium

246
Q

Where is calcitonin produced

A

Thyroid C-cells (parafollicular)

247
Q

What causes the release of calcitonin

A

Hyoercalcaemia

248
Q

Action of calcitonin

A

Inhibits bone resorption by direct effect on osteoclasts

249
Q

3 factors inhibit insulin release

A

alpha-adrenergic drugs, beta-blockers, sympathetic stimulation.

SUGER (17 decks)

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