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Third stage
Medicine
Lec-2
د
.
محمد
خالد
1/1/2014
ENDOCRINOLOGY
Definition
The science dealing with endocrine glands and their disorders.
HORMONES
• Chemical messengers
• Directly released from endocrine cells into the circulation.
• Acting at a distant site.
• Recently other functions were discovered:
1. Neurotransmittors
2. Local action on adjacent cells (paracrine action)
3. Direct action on the cells of origin (autocrine action).
How hormones act?
• By binding to specific receptors on cell surface or within the cell.
• Followed by a cascade of intracellular reaction leading to response.
The Hypothalamic & Pituitary Control
HYPOTHALAMUS
- Functions:
• Circadian rhythm
• Regulate menstrual cycle
• Stress situations
• Mood regulation
• Control pituitary gland function
The Pituitary Gland
• Anterior pituitary Hs. are stimulated or inhibited by the hypothalamus
• Posterior pituitary Hs:
1. ADH (vasopressin) and oxytocin are synthesized in the supraoptic and
paraventricular parts of the brain.
2. They then pass to the posterior pituitary along a single axon of the producing cells to
be stored there.
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1- GnRH [+] LH, FSH Ovaries & testes Ovulation & estrogen Spermatogenesis &
testosterone
feed-back: Estrogen, Progesterone, Androgen, & Prolactin
2- GHRH [+] GH Many tissues many functions & Growth
feed-back: IGF-1
3- Dopamine [-] PROLACTIN Breasts & gonads Lactation
feed-back: estrogen
4- TRH [+] TSH Thyroid Thyroxin, metabolism
feed-back: T3
5- CRH [+] ACTH Adrenals steroids, Stress
feed-back: Circadian rhythm, Stress, Cortisol
6- Vasopressin (ADH) Distal convoluted tubule Water balance
feed-back: Osmolality, Intravascular volume.
7- Oxytocin Breast & uterus uterine contraction, Lactation
feed-back: Delivery
Control and feedback
- The Hs. secreted from the target glands
feedback to the pituitary تغذية استرجاعية
- Feedback is the mechanism of control of most of hormones.
- Feedback can be:
• Negative = inhibitor
• positive =stimulatory
Hormone-producing tumors does not respond to feedback (this is useful in diagnosis).
Obesity
• Is a condition in which excess fat accumulates in the body mostly in subcutaneous
tissue.
• It occurs when dietary intake exceeds energy expenditure.
• It is a common problem that can be defined by using the body mass index which is the
body weight in kilograms over the square of the height in meters.
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• The body mass index: weight (kg)
square of height (m
2
)
Nutritional status in relation to body mass index:
• Underweight < 18.5
• Normal 18.5 - 24.9
• Overweight 25 - 29.9
• Obese 30 – 39.9
• Morbid obesity
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What cause obesity? It is a matter of how much energy obtained & how much we spend it.
Obesity is considered an important clinical condition because it is a risk factor for many
diseases such as type II D.M., hyperlipidemia, hypertension, atherosclerosis & metabolic
syndrome X.
Sleep apnoea which means stop breathing during sleep & it is common in the very obese
persons.
Obesity also may lead to gastro-oesophageal reflux diseases.
Obesity lead to increase risk of cancer of the breast, prostate,colon & endometrium, but
80% of the human obesity is due to genetic factors.
We have the hormone leptin which is secreted by some subcutaneous adipose tissue in
response to fat storae & it is centrally act to promote satiely & increase body metabolic rate
so it suppress appetite.
Congenital leptin deficiency accounts for 1-3 % in early onset morbid obesity.
Other hormone called ghrelin which is secreted by the tissue of an empty stomach to
stimulate appetite by its action on the hypothalamus.
When a person is subjected to gastric surgery, this will lead to decrease ghrelin & therefore
decrease appetite (poor appetite).
Also we have melanocyte stimulating hormone (MSH) which has a role in controlling
appetite & satiety i.e. regulate hypothalamic control of food intake.
Cushings syndrome: a condition related to endocrine & obesity, in which there is an
increase in cortisol activity lead to central obesity with large face (moon face) &
supraclavicular fat accumulation.
Menopause is associated with a decrease in the basal metabolic rate which increases the
body weight but weight gain is greatest in perimenopausal period (around 45 years).
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Metabolic syndrome X: is a condition in which people tend to have intraabdominal or
central obesity & those people develop insulin resistance leading to hyperinsulinaemia but
at the same time β- cells of the pancreas will be exhausted & develop impaired glucose
tolerance & type II D.M.
Other feature is arterial hypertension, there will be hypertriglyceridemia & decrease in high
density lipoprotein cholesterol (HDL) which in turn lead to atherosclerosis.
Other condition lead to obesity is polycystic ovarian syndrome which occur more frequently
women child bearing age (around 15-20 years ) so they tend to have obesity, infertility &
the ovary on US show multiple cyst & it may have some relation to metabolic syndrome &
amenorrhoea.
Hypothalamic obesity in which there is 1-2%of the morbidly obese persons have been
found to lack leptin & when they treated with leptin, they dramatically have weight
reduction.
Weight loss
If the loss is > 3kg in couple of months it is significant & there may be a disease.
Causes of weight loss:
o Psychiatric, anorexia nervosa, depression
o Systemic diseases:
Tuberculosis
Recurrent infection
HIV / AIDS
o Uncontrolled D.M.
o Hyperthyroidism
o Addisons disease
o GIT diseases:
Malabsorption
Helminthes infection
o Malignant diseases:
o Depression of appetite due to renal failure
o Parasites: (taenia saginata)
If the person says that he eats too much but loses weight so we can expect that he
probably has hyperthyroidism, parasite infection (Taenia Saginata), type I.D.M. or
malabsorption syndrome.