Endocrinology Flashcards
1
Q
What are hormone plasma carriers?
A
A reservoir of inactive hormone, providing hormone reserve. Don’t degrade or get uptaken and thus allow smooth fluctuations in hormones over time. Only the free hormone contributes to feedback and is biologically active
2
Q
Which type of hormones are transported freely in plasma?
A
Catecholamines
Steroid hormones are hydrophobic-bound to steroid binding protein. Only small amounts of free hormone dissolved in plasma
3
Q
Which receptors do hydrophilic or hydrophobic hormones bind to?
A
Hydrophilic-cell surface receptors
Hydrophobic-nuclear receptors
4
Q
What are the main functions of the hypothalamus?
A
Temperature regulation (anterior hot, posterior, cold)
Neuroendocrine function: Catecholamines, ADH, oxyocin, TSH, ACTH, FSH, LH, prolactin, growth hormone
Appetite behaviours Thirst, hunger and sex
Defensive reactions: fear and rage
Control of body rhythms
5
Q
How does the hypothalamus sense the thirst response?
A
Hypertonicity via osmoreceptors. Hypovolemia sensed by baroreceptors releases angiotension II.
Both of which act on hypothalamus to produce thirst.
Thirst may occur without decreased osmolality due to haemorrhage
6
Q
What is released in the posterior pituitary?
A
Oxytocin
ADH (vasopressin)
Both PRODUCED in posterior pituitary but also exist in neurones
Both not bound in plasma
7
Q
What are the key actions of oxytocin?
A
Contraction of myoepithelial cells allowing milk expression
Smooth muscle contraction of uterus
Inhibited by progesterone
Increased number of oxytocin receptors in uterus rather than increased oxytocin levels in labour
8
Q
Which hormones are secreted by the anterior pituitary?
A
ACTH: aldosterone +sex hormones
GH: somatomedins. Produces a fall in blood urea nitrogen
TSH: thyroxine
FSH: growth of ovarian follicle/maintenance of corpus luteam/ testes
LH: growth of ovarian follicle/maintenance of corpus luteam/ testes. Acts on theca internal cells.
Prolactin: breast milk
No nerves involved in anterior pituitary
9
Q
Why do dopaminergic drugs cause breast development?
A
Prolactin is under constant inhibition by hypothalamus via dopamine, reducing inhibition causes secretion
10
Q
Why do patients with Addison’s disease/primary adrenal insufficiency get tanned?
A
ACTH binds to melanotropin, acts as MSH (melanocyte stimulating hormone). With adrenal insufficiency there increased release of ACTH
11
Q
What are the actions of growth hormone?
A
A proportion of GH is protein bound in plasma
Decreased insulin sensitivity
Na+ retention
Lipolysis
Erythropoesis
Protein synthesis
Epiphysial growth (mitosis)
Does not affect carbohydrate utilization. Does not stimulate pancreatic B cells to release insulin, just increases ability of pancreas to respond to insulinogenic stimuli. Can produce ketosis in excessive amounts
12
Q
Which stimuli increase/decrease GH release
A
Hypgylcemia, exercise, fasting, going to sleep, protein meal, stressful stimuli, L-dopa, estrogens and androgens, glucagon all increase GH release
REM sleep, glucose, cortisol, GH and IGF-1 all decrease GH release
13
Q
What are the effects of hypopituitarism?
A
Decreases activity of other endocrine glands
Increased insulin sensitivity
Diabetes insipidus: increased osmotic load due to ACTH deficiency, TSH deficiency causes low metabolic rate and GH deficiency causes depression of glomerular filtration rate
Glucocorticoid deficiency
14
Q
How does the histology of the thyroid change when it is active vs inactive?
A
Inactive: colloid( glycoprotein and thyroglobulin) abundant, follicles are very small cubiod cells
Active: Follicles columnar and larger with much smaller areas of colloid with reabsorption lacunae
15
Q
What is the difference between T4 and T3?
A
T4: primary hormone secreted
T3: greater activity, generated at sites of action by peripheral tissues by deiodination
Iodine required to make thyroid hormones. Taken up by the thyroid across basement membrane by Na/I symporter and across apical membrane by Cl/I exchanger
16
Q
How does colloid serve as a reservoir for thyroid hormone?
A
Thryocytes make thryoglobulin. Thryoid hormones produced are bound to thyroglobulin until required to be released as T3 and T4
17
Q
What are the functions of thyrocytes?
A
- Collect and transport iodine
- Synthesis thryoglobulin and endocytosis into colloid
- Fix iodine to thyroglobulin and generate thyroid hormones
- Remove thyroid hormones from thyroglobulin and secrete them into the circulation
18
Q
How do thyroid hormones travel in plasma?
A
Protein bound as lipophilic
Free forms in plasma are in equilibrium with protein bound hormones
19
Q
Which proteins bind to thyroid hormones?
A
TBG: highest affinity but smallest capacity. Raised in pregnancy
Transthyretin
Albumin: greatest binding capacity
20
Q
How do hyperthyroidism, hypothyroidism, estrogens and glucocorticoids/androgens affect thyroid levels?
A
Hyperthyroid: binding N total plasma H free plasma H
Hypothyroid: binding N total plasma L free plama L
Estrogens/heroin: binding H total plasma H free plasma L
Glucocorticoids/androgens: binding L total plasma L free plasma N
21
Q
Which tissues do thyroid hormones NOT increase O2 consumption in?
A
Brain Testes Uterus Spleen Lymph nodes Anterior pituitary
22
Q
Why does hyperthyroidism lead to increased urine K+ and uric acid secretion?
A
Catabolism of endogenous protein and fat stores without increased food intake. Also causes low circulating cholesterol
23
Q
How does hyperthyroidism affect the kidneys?
A
Raised body temperature-> cutaneous dilation-> decreased peripheral resistance-> increased reabsorption of Na and H20
Affect erythropotein
24
Q
How do increased thyroid hormones affect the heart?
A
Increased cardiac output
Increased heart rate
Increased contractility and pulse pressure
25
How does hyperthyroidism affect the CNS?
Rapid mentation
Irritability
Restlessness
Shortens stretch reflexes
26
How does hyperthyroidism affect the GI tract?
Increased absorption of carbohydrates
| Plasma glucose increases rapidly after a meal then decreases rapidly again
27
Why do beta blockers work in thyrotoxicosis?
Thyroid hormones have a similar action to catecholamines
28
What are the 3 layers of the adrenal cortex and what do they excrete?
From outside to inside, salt, sugar sex
zona glomerulosa: Aldosterone
Zona fasciulata: Glucocorticoids/ cortisol
Zona reticularis: Androgens
All made from cholesterol
29
What does the adrenal medulla excrete?
Adrenaline, noradrendaline and dopamine
Both made from tyrosine
Secretion initiated by ACh
30
What are the affects of catecholamines?
Glycogenolysis in liver and skeletal muscle
Mobilisation of free fatty acids
Increased plasma lactate
Stimulation of metabolic rate
Increased cardiac contractility and heart rate, increased excitability
NA: vasoconstriction (a1), HTN, stimulating baroreceptors producing rflex bradycardia, decreasing CO and increasing TPR=normal pulse pressure
A: Vasodilation in skeletal muscle and liver (b1). Usually overbalances constriction affect of NA and decreases TPR
31
What causes adrenal hyperplasia?
Any enzyme deficiency in adrenal system
32
What happens in cholesterol desmolase deficiency?
Adrenal hyperplasia
| Female genitalia regardless of sex
33
What happens in 3bhydoxysteroid dehydrogenase deficiency?
Increased DHEA
| Not sufficient to cause masculisation in females but hypospadias in males
34
What happens in 17a-hydoxylase deficiency?
No sex hormones
Female external genitalia
elevated corticosterone and aldosterone thus HTN & hypokalaemia
35
What happens in 21b-hydoxylase deficiency?
Decreased cortisol and aldosterone
| Virilisation due to androgens
36
What happens in 11b-hydoxylase deficiency?
Virilisation and salt retention
37
How are glucocorticoids bound in plasma and when to the inhibit the pituitary?
Bound to CBG in plasma
| Only free cortisol inhibits anterior pituitary
38
Who is adrenal estrogen most important for?
Men and postmenopausal women
39
What are the affects of gluccocorticoids (cortisol)?
Increased protein catabolism, hepatic glycogenesis and gluconeogenesis
Raises plasma glucose
Allows for vascular smooth activity
Decreases lymphocyte, eosinophil and basophil count, increases neutrophils, platelets and RBC
Low GCs causes irritability, apprehension, defective water excretion
40
What are the signs of cushing syndrome?
```
Protein catabolism
Thick skin and hair
Poor muscle
Poor wound healing
Acne
Hirsituism
Fat redistribution
Striae
HTN
DM
Osteoporosis
```
41
What do mineralocorticoids/aldosterone do?
Increases reabsorption of sodium from urine, sweat, saliva and colon thus retention of Na in ECF
42
What are some conditions that increase aldosterone secretion?
```
Surgery
Anxiety
Trauma
Haemorrhage
(All have increased glucocorticoid secretion as well)
High K+ intake
Low Na+ intake
Constrictin of inferior vena cava in thorax
Standing
Secondary hyperaldosetonism (HF, CKD)
(Glucocorticoid secretion unaffected)
```
43
What are the key elements involved in changing dehydrocholesterol into calcium?
Sunlight
Liver
Kidney
Cholesterol is converted into Vitamin D by sunlight. Vitamin D increases calcium and phosphate uptake from the GIT. High calcium inhibits renaal 1a-hydroxylase so less 1,25-DHC is produced
44
Describe the parathyroid hormone and calcium feedback loop?
Plasma calcium drops
Increased PTH secretion
Acts to increase Ca reabsorption in kidney and bone plus increase 1.25-DHC formation in kidney
Decreases urinary excretion of Ca (increased phosphate excretion)
Increased release of calcium into plasma
High circulating Ca and 1,25-DHC decrease PTH
45
Where is PTH produced?
Chief cells of parathyroid gland
46
What is renal hyperparathyroidism?
Hypocalcemia due to inability of kidneys to produce 1,25-DHC
47
Where is calcitonin produced and what are its actions?
Produced by parafollicular (c-cells) of thyroid
Lowers circulating Ca and Po4 levels
Lowers Ca by inhibiting bone resorption
48
What affect does cortisol have on the stomach?
Increases HCL secretion and pepsin
49
Why is the adrenal medulla considered a modified sympathetic ganglion?
Receives preganglionic input
| Embryologically arises from same origin as sympathetic nerve
50
What are the key effects of adrenaline?
```
Increased glyconeogenesis from liver and muscle
Mobilise FFA from adipocytes
Increase BMR
Increase pulse pressure
No effect on protein synthesis
```
51
What is the physiological response to activation of adrenergic nervous system?
1. Increase circulating renin levels
2. arteriolar coronary dilation
3. hepatic glycogenolysis
52
Where are alpha adrenergic receptors found?
Intestinal smooth muscle
Cutaneous vascular smooth muscle
Pupils
Sweat glands
53
What are the effects of a B2 antagonist?
Bronchoconstriction
Coronary constriction
Peripheral vasoconstriction
Bradycardia
54
Why are alpha adrenergic blockers used in refractory shock?
Increase renal blood flow
| Prevent imbalance between pre capillary and venular tone
55
What is the effect of injected dopamine?
Renal vasodilation
Inotropic affect on heart via B1 receptors
General vasoconstriction, hence net increase in total peripheral resistance
Decrease appetite via dopaminergic receptors
NO effect on prolactin
56
Why does the thyroid enlarge in pregnancy?
HCG looks similar to TSH in structure
57
How is iodine utilised by the thyroid?
Essential for making thyroid hormone
About 80 micrograms enters thyroid per day by active transport via NIS symporter and pendrin
Most of the iodine ingested is just excreted by the kidneys
58
How does thyroid affect growth?
Essential for bone growth and epiphyseal closure
59
Where is most calcium in the body?
99% in the bone
Some readily exchangeable
Most is slowly exchanged by bone resorption and absorption
60
What facilitates absorption of calcium?
1,25 dihydroxycholecalciferol
61
How is calcium filtered by the kidney?
99% reabsorbed
60% in proximal tubule
PTH acts at distal tubules to reabsorb calcium
62
Which hormones affect calcium levels in the blood?
1, 25 dihydoxycholecalciferol: increases calcium absorption from intestine
PTH: from parathyroid gland, releases Calcium from bones and increases phosphate excretion in urine
Calcitonin: decreases osteoclasts and decreases calcium levels
63
How does pH affect calcium?
High pH-> plasma proteins more ionised->easier for Ca+ to bind-> worse hypocalcemia
ie. patient with tetany hyperventilates, becomes more alkalotic, worsens tetany
64
What are the key actions of phosphorus?
Used in ATP cAMP
Absorbed in the duodenum and small intestine by active transport and passive diffusion
85-90% reabsorbed in the kidney
65
What are the 2 types of bone?
Cortical bone: 80% of all bone, outer layer, haversian canals
Spongey bone: 20%, nutrition via diffusion
66
What are the 2 ways bones form?
Chondral ossification; cartilage first, then bone
| Membranous ossification; tissue first, then bone
67
Which hormones affect the width of the epiphyseal plate between epiphysis and diaphysis?
GH
IGF-1
Bone continues to grow as long as the plate does not fuse with the shaft (cartilage cells proliferate, release VEG-F-> causes ossification)
68
What are the haematological origins of osteoclasts and osteoblasts?
Osteoblast: from fibroblasts, lays down bone
Osteoclast: from monocytes, eats away bone
69
How much of the adult skeleton is remodelled?
18% per year
70
Why does menopause cause osteoporosis?
Estrogen increases production of TGF-B-> apoptosis of osteoclast
Estrogen decreases production of TNF-A->osteoclasts break down bone
Low estrogen->hormones act unopposed-> osteoclasts get out of control->osteoporosis
71
What are the key actions of calcitriol/vit D?
Increase Ca-H ATPase -> Increase calcium and phosphate reabsorption
Via intestinal cells and kidney
Decreases pTH secretion
72
Factors that increase 1,25 dihydoxycholecalciferol
```
PTH
Low calcium
prolactin
growth hormone
calcitonin
```
73
What increases release of PTH?
```
Low levels of calcium
Low Mg
cAMP
High phosphate
Chronic renal disease
```
74
What are the actions of PTH?
Mobilise calcium
Increase calcium absorption from intestine
Increase distal reabsorption of kidney
Increases proximal reabsorption of phosphate, in excess can cause hypophosphatemia
75
How does chronic kidney disease cause secondary hyperparathyroidism?
```
Vit D can't be activated
Reduced calcium absorbed from intestine
Plasma Ca chronically low
PTH chronically high
Causes hypertrophy and hyperparathyroidism
```
76
What causes hypercalcemia of malignancy?
20% due to bone lesions
| 80% due to elevated PTHrP (common in cancer of breast, ovary, kidney, skin)
77
What causes calcitonin secretion?
High calcium
Gastrin
CCK
Secretin
Calcitonin lowers calcium
78
What are the 4 types of cells in the pancreas? What do they secrete?
A: Glucagons (catabolic, moves glucose and FFA into blood stream)
B: Insulin (moves glucose into cells)
D: Somatostatins (turn everything off)
F: Pancreatic polypeptides
79
Where is insulin made?
Rough endoplasmic reticulum
Transported to golgi apparatus
Packed as proinsulin
Once activated, split by C-protein into insulin
80
What stimulates insulin release?
Glucose >5mmol/L
Anything that increases cAMP (glucagon + theophylline+B-agonists)
Vagal stimulation (via Ach)
GIT hormones (GIP, enteroglucagon, secretin, CCK)
Oral hypoglycemic drugs
81
What decreases insulin release?
```
Somatostatin
Beta blockers
Sympathetics
K+ depletion
Galanin
Insulin (via negative feedback)
```
82
What are the actions of insulin on lipids?
Brings glucose and K+ into cell
Increase lipoprotein lipase so increases FFA storage
Decreases enzyme lipase which normally breaks down fat
83
What is the action of insulin on muscles?
Brings glucose, K+ and ketones into the cell
Makes glycogen for storage
Makes more proteins and decreases protein catabolism
Decreases release of glucogenic amino acids
84
What action does insulin have on the liver?
Increased protein synthesis and fat deposit
Decreased ketogenesis
Decreased glucose output due to increased glycogen synthesis
Increased cell growth
85
How does insulin differ from growth hormone?
decreases hormone sensitive lipase in fat cells
| increases lipoprotein lipase in the vicinity of fat cells
86
What are the key effects of insulin deficiency?
Diminished growth
Reduced lipogenesis
Diabetes mellitus
87
What are the 4 places where glucose uptake is not affected by diabetes mellitus?
Intestinal absorption ->via SGLT1 and 2
Reabsorption of glucose in proximal tubule ->via SGLT 1 and 2
Brain
RBC
88
What is the fate of most ingested glucose?
50% of ingested glucose is burned to CO2 and H2O
5% converted to glycogen
30-40% converted to fat to be deposited
Therefore with increased glucose in diet, most will be stored as fat
In diabetes glucose just stays in the blood, hardly any converted to fat
89
Why do diabetics drink a lot?
Blood full of glucose so hyperosmolar
Glycosuria and polyuria due to osmotic diuresis. Increased Na and K+ lost in urine with glucose
Causes dehydration and polydipsia
90
Why do diabetics get muscle wasting?
Cells have no glucose
Body thinks it's starving
Liver releases glucose and so does skeletal muscle
Diminished protein synthesis and wasting
91
Why do diabetics have increased ketones?
```
Fat catabolism is increased
Increased FFA
Excess acetyl CoA is fomred
Acetyl CoA is converted into ketones
Ketones cause acidosis
```
92
What increases glucagon release from the gut?
Hypoglycemia (exercise, stress, infection)
Amino acids (alaine, serine, glycine)
CCK and gastrin
Cortisol
Vagus nerve activity
Alpha receptors (-) and beta receptors (+) ->balance is stimulation
93
What decreases glucagon release?
```
Glucose and insulin
GABA (released along with insulin)
Somatostatin
Secretin
FFA and ketones
Alpha adrenergic agents
```
94
What are the key actions of glucagon?
```
Main site of action liver
Glycogen breakdown
Gluconeogenesis
Ketogenesis in liver
Increased lipolysos in adipose
In large dose it is a +ve inotrope
Increased secretion of insulin and GH
Calorigenic via increased hepatic clearance of amino acids
NO EFFECT ON MUSCLE
```
95
what controls GH release?
GHrH (+)
| Somatostatin (-)
96
Which receptors does GH act on?
Tyrosine kinase activities
Type 1->binds IGF-1 > IGF-II> insulin
Type 2 -> binds IGF-II > IGF-1
Insulin receptors -> binds insulin > IGF 1
IGF-II more important in fetus
97
What does the prolactin?
Promotes milk secretion (not ejection)
Decreases actions of LH and FSH. Can cause infertility in males and females
Role in males unknown
98
What increases prolactin release?
```
Nipple stimulate in non-lactating women (via T5)
Stress
Pregnancy
TRH
Vasopression
Estrogen
```
99
What decreases prolactin release?
L-dopa
Bromocriptine
Apomorphine
100
What are the key actions of ADH/vasopression?
Inserts aquaporin into collecting duct of kidney
No affect on distal tubules
Water reabsorption is passive
Increases permeability of inner medulla of kidney to urea
Vasoconstriction in vasa recta of renal medulla causing decreased blood flow
Increases ACTH release by anterior pituitary
101
What increases ADH/vasopressin release?
Mild hyperosmolality of ECF
Severe hypovolemia
Mild hypovolemia and mild hyperosmolality of the ECF
Severe hypovolemia + severe hypoosmolality of ECF
Drugs (morphine, nicotine, chlorpropamide)
Stress, pain, exercise, sleep
Standing, N+v
Post op (pain, morphine and loss of ECF)
102
What decreases ADH/vasopressin release?
Alcohol (water + alcohol in beer inhibit ADH release). Has no effect on tubular Na reabsorption
Increased plasma volume
Decreased plasma osmotic pressure
Controlled by osmoreceptor in hypothalamus and low pressure receptor in veins and atria
103
Why in SIADH may urine volume/day be normal?
With SIADH secretion the GFR may be increased
104
What are the two types of diabetes insipidus and how are they different?
Central : not enough ADH released
| Nephrogenic: Kidney doesn't respond to ADH
105
What causes thirst?
```
Controlled by hypothalmic mechanism
Caused by intracellular dehydration
Caused by extracellular dehydration
Increased with haemorrhage/low CO
Increased by High ANGII levels
Increased by increased osmolarity due to high sodium
```
106
Why can thirst occur without a change in plasma osmolarity?
Haemorrhage increases thirst via angiotensin via osmoreceptors
107
What happens if you drink 10L of water in 5 minutes?
Immediate expansion of ECF
Increase in interstitial fluid volume
Altered consciousness as cerebral neurons swell
Spontaneous haemolysis will occur when osmolarity <20mOsm/kg
Urea is freely diffusible and obtains equilibrium with ECF without any significant changes in its concentration in plasma
108
What increases secretion of oxytocin?
Mechanical distension of vagina
| Stimulation of nipples
109
What does the pineal gland do?
Outside blood brain barrier
Secretes melatonin (made from tryptophan via serotonin)
Has no influence over K+ metabolism
110
How does GnRH affect LH?
In general increased GnRH will increase LH +FSH secretion from anterior pituitary
Constant GnRH high is ineffective due to receptor downregulation
An hourly pulse will increase LH secretion
111
What does FSH do in the male?
Stimulates seminiferous tubules to make sperm
Stimulates sertoli cells to control maturation of spermatids to spermatozoa
Increases production of inhibin which acts as negative feedback on pituitary
112
What does LH do in the male?
Trophic on interstitial leydig cells-> stimulates androgen production
113
What does FSH do in the female?
Accelerates growth of 6-12 primary follicles with proliferation of granulosa cells +theca interna and externa (follicle maturation)
In the hours before ovulation there is a rapid spike in LH +FSH
114
What does LH do in the female?
Acts via receptors on theca interna cells_> stimulate ovulation and luteinisation of ovarian follicle
For final development of the follicle and ovulation
LH converts the granulosa and theca interna cells into a progesterone secreting type of cell
115
What are the effects of testerone?
Increases growth, protein synthesis
Retention of Na, K, phosphate, Calcium and water
Increase libido
Maturation of wolffian ducts and male internal genitalia
116
Where is testerone excreted?
Metabolised in liver and excreted in urine
| Can also be converted into DHT from 5a-reductase
117
How is testerone related to development?
Elaborated in male embryo from 7th to 12th weeks
Almost absent in the male up to 10 years
Excreted in the female in small amounts
Necessary for normal spermatogensis
Produced from cholesterol in leydig cells
118
What are the key affects of estrogen?
1. Increases uterine muscle and amount of contractile proteins
2. Changes vaginal epithelium from cuboidal to squamous
3. Makes cervical mucus thinner and alkaline
4. Makes boobs grow in puberty
5. Increases osteoblastic activity
6. Increased secretion of thyroid binding globulin ->euthyroid
7. Slight increase in total body protein
8. Increased secretion of angiotensinogen
9. Sensitises myometrium to oxytocin
10. Increases deposition of subcutaneous fat
11. Causes skin to be softer, smoother and more vascular
12. Decreases FSH and may increase/decrease LH
119
Where is progesterone secreted?
Placenta and corpus luteum
In last half of pregnancy the placenta secretes enough progesterone to keep pregnancy going so corpus luteum secretion not necessary
120
What are the key effects of progesterone?
Decreased excitability of myometrial cells
Thickens mucus and makes cervix firmer
Stimulates breast lobules and alveoli
Causes vaginal epithelial proliferation and thick viscous mucus production
Raises temperature and probably responsible for temp rise at ovulation
121
Why does oophorectomy before the 6th week of pregnancy lead to abortion?
The placenta is not able to produce enough estrogen and progesterone to maintain pregnancy
122
What occurs during the follicular phase of the menstrual cycle?
Progesterone levels are depressed
Oestradiol secretion is steady NOT inhibited
Vaginal mucus is thin and alkaline
Basal body temperature is not elevated
123
How do LH and FSH develop the ovarian follicle?
Both essential for ovulation
Granulosa cells initially have FSH receptors, but later develop LH receptors
Both rise in hours before ovulation
LH converts granulosa cells and theca interna cells into progesterone secreting type of cell
124
When are plasma oestrogen levels the highest?
24-48 hours pre ovulation
125
How does the ovary self regulate?
Theca interna provides androgens to granulosa cells and estrogens which inhibit GnRH, LH and FSH
Granulosa cells secrete inhibin which inhibits FSH release
LH regulates thecal cells, granulosa cells regulated by both LH and FSH
126
When is the number of oxytocin receptors the highest?
The amount of oxytocin receptors in the myometrium abd decidua increase 100 fold during pregnancy and reaches a peak during early labour
127
What is relaxin and what does it do?
Relaxin is produced by corpus luteum, uterus, placenta and mammary glands in women and prostate glands in men. During pregnancy it relaxes the pubic symphysis and dilates uterine cervix.
In men it is found in semen
128
How do endocrine glands change in pregnancy?
Anterior pituitary: 50% increase in size with increased secretion of corticotrophin, thyrotropin and prolactin
Adrenal: increased glucocorticoid secretion,2x increased aldosterone secretion
Thyroid:50% increase in size and production of thyroxine (from increased human chorionic gondotropin and placental human chorionic thyrotropin)-but euthyroid
Parathyroid: increased size and secretion of PTH (especially in lactation)
129
What are the key physiological changes noted in pregnency?
Uterus increases 22x
15% increase in basal metabolic rate in second half of pregnancy
Increased absorption and storage of protein
Minute ventilation increases 50% with a fall in arterial pCO2
RR increases as diaphragm squished by baby
Increased urine production, increased fluid, Na and Cl reabsorption
CO increased by 30-40% by 27th week, but then normalises
Blood volume increases in 2nd half of pregnancy
Decreased maternal antibody production
130
What are the actions of human horionic somatomammotropin?
Similar to that of GH
131
Where is oestiol synthesized during pregnancy?
Combined effect of fetal and placental tissue
| Level is higher at 36th week than 20th week
132
What is the theory behind why the maternal body does not reject the fetus?
Placental trophoblast lies between fetal and maternal tissue and does not express MHC genes so antibodies to fetal proteins do not develop
133
What are the key placental hormones?
Placenta secretes, hCG, progesterone, estrogen, corticotropin releasing hormone, melanocyte stimulating hormone, leptin, human chorionic somatomammotropin
hCG vital to prevent expulsion of implanted ovum
134
Why does lactation only start after birth?
Breast duct growth is stimulated by estrogens, but this estrogen antagonises the milk producing affect prolactin
After expulsion of placenta, levels of estrogen and progesterone abruptly decline which initiates lactation
