Summary
Summary A100
- Module
- A100
- Institution
- Oxford University (OX)
Endocrinology is the study of hormones. Hormones are essential for our every-day survival. They control our temperature, sleep, mood, stress, growth and more.
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EndocrinologyCONTENTS Endocrine diseases 214
Sex hormones 199 Puberty 218
Hypothalamic hormones 203 Endocrine changes in pregnancy 220
Pituitary gland hormones 205 Placental hormones 220
Thyroid gland hormones 209 Labour 223
Adrenal hormones 210 Puerperium and lactation 224
Renin-angiotensin system 212 Fetal and neonatal endocrine system 226
Pancreatic hormones 213
S e x h o rm o n e s
1. T h e o va ry secretes 11 h o rm o n e s (by d e fin itio n a ‘h o rm o n e ’ is a substance p ro d u ce d and
secreted by a gland o r fro m ce ll(s)/tissues) in to th e b lo o d stream th a t circu la te s and acts
a t a ta rg e t site re m o te fro m th e source. T hu s o varian prostaglandins are s tric tly pa ra crin e
substances (Fig. 6.1)
2. A n d ro g e n s in fem ales are p ro d u ce d by
® O vary = 25%
® Adrenal glands = 25%
® Peripheral conversion o f androstenedione = 50%
3. M arke rs o f co rp u s lu te u m fu n c tio n are
® 17-hydroxyprogesterone (n o t secreted by placenta)
• Relaxin
4. O e stro g e n
® 3 naturally occurring oestrogens
i. O e stro n e (E1) — produced in menopause
ii. O e stra d io l (E2) - prim ary oestrogen in non-pregnant w om en
iii. O e s trio l (E3) — prim ary oestrogen in pregnancy
® O e stra d io l is th e m ost active o f th e natural oestrogens
® Produced by
i. D eveloping follicles in ovary
ii. C orpus luteum
iii. Placenta
iv. Liver
v. Adrenal glands
,Figure 6.1 Ovarian horm ones
vi. Breast
vii. Adipocytes
• In plasma binds to
i. Sex horm one-binding globulin (SHBG)
ii. A lbum in
• M etabolized in th e liv e r to oestrone and o e strio l (fig. 6.2)
• Excreted in th e kidney as o e strio l glucuronide
• Has 2 main receptors subtypes (o th e r re c e p to r subtypes exist)
i. a (found in endothelial cells)
ii. p
• W o r k by genom ic expression
Figure 6.2 Metabolism o f oestradiol
5. O e s tro g e n fu n ctio n s
• Cardiovascular
i. Vasodilator (via an increase of N O S leading to an increase in N O )
ii. Prevents atherosclerosis
• Bone
i. Maintenance o f bone density - decreases resorption of bone by antagonizing PTH
ii. Fusion of epiphyseal plates
• Increases clotting by
i. Increasing levels o f factors II, VII, IX, X , and plasminogen
ii. Decreasing a n ti-th ro m b in 3
iii. Increase platelet adhesiveness
• G astrointestinal
i. Decrease m o tility o f bow el
ii. Increases bile pro d u ctio n
• M etabolic changes
i. Increases high-density lipoprotein (H D L ) levels
, ii. Decreases low -density lip o p ro te in (LD L) levels
iii. Decreases cholesterol levels
iv. Increases T A G synthesis
• Stimulates pigm entation o f skin by increasing phaeomelanin
i. N ipple
ii. A re o la
iii. G enital regions
• Proliferation o f endom etrium
• Causes N a + and H 20 re te n tio n b y kidney
P ro g e ste ro n e
• Sources
i. Dioscorea mexicana (a typ e o f plant)
ii. C orpus luteum
iii. A drenal glands
iv. Placenta
» Stored in adipose tissue
® In plasma binds to
i. C o rticoste ro id -b in d in g globulin (CBG)
ii. A lbum in
• M etabolized in liv e r to pregnanediol
® Excreted by kidney as pregnanediol glucuronide
» Levels
i. Pre-ovulation = < 2 ng/mL
ii. Post-ovulation = 5 ng/mL
iii. A t te rm = 100-200 ng/mL
® A t te rm placenta produces 250 m g/day progesterone
Progesterone functions
® Uterus, cervix, and vagina
i. C onverts pro life ra tive to se cre to ry endom etrium
ii. W ith d ra w a l o f progesterone causes m enstruation
iii. Thickens cervical mucus
iv. Inhibits ute rin e c o n tra ctio n u n til te rm
• Increases co re te m p e ra tu re fo llo w in g ovulation
• Sm ooth muscle relaxant
® Catabolic (thus causes an increase in appetite)
• Increases aldosterone p ro d u ctio n (leading to N a+ and H 20 rete n tio n )
• Reduces pressor responsiveness to angiotensin-2
• Respiration
i. Increased v e n tila to r response t o C 0 2
ii. Decreased arterial and alveolar p C 0 2
® Inhibits lactation during pregnancy
® N e u ro p ro te c tiv e (is being investigated in tre a tm e n t o f m ultiple sclerosis; dem yelination halts
during pregnancy)
Inhibins
® A re peptide m em bers o f transform ing g ro w th fa cto r (TGF)-(J family
• T here are 2 form s o f inhibin
i. Inhibin A
ii. Inhibin B
« A re secreted by ovarian granulosa cells
» Selectively in h ib it FSH secretion b u t n o t LH secretion
A
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