endocrine

ENDOCRINOLOGY

Dr: Mohammed Khalid

DefinitionThe science dealing with endocrine glands and their disorders. HORMONES Definition• Chemical messengers• Directly released from endocrine cells into the circulation.• Acting at a distant site.• Recently other functions were discovered:1. Neurotransmittors2. Local action on adjacent cells (paracrine action)3. Direct action on the cells of origin (autocrine action).

How hormones act ?

1. By binding to specific receptors on cell surface or within the cell. 2. Followed by a cascade of intracellular reaction leading to response.

The Hypothalamic & Pituitary Control

HYPOTHALAMUS - Functions: 1. Circadian rhythm 2. Regulate menstrual cycle 3. Stress situations 4. Mood regulation 5. 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.

GnRH [+] LH, FSH Ovaries & testes Ovulation & estrogen Spermatogenesis & testosterone-feed-back: Estrogen, Progesterone, Androgen, & Prolactin• GHRH [+] GH Many tissues many functions & Growth -feed-back: IGF-1• Dopamine [-] PROLACTIN Breasts & gonads Lactation -feed-back: estrogen

TRH [+] TSH Thyroid Thyroxin, metabolism -feed-back: T3• CRH [+] ACTH Adrenals steroids, Stress -feed-back: Circadian rhythm, Stress, Cortisol•Vasopressin (ADH) Distal convoluted tubule Water balance -feed-back: Osmolality, Intravascular volume.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. The body mass index: weight (kg) square of height (m2)

Nutritional status in relation to body mass index:

Underweight < 18.5 Normal 18.5 - 24.9Overweight 25 - 29.9 Obese 30 – 39.9Morbid obesity  40

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).

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: Psychiatric, anorexia nervosa, depression Systemic diseases: Tuberculosis Recurrent infection HIV / AIDS


Uncontrolled D.M. HyperthyroidismAddisons disease GIT diseases: • Malabsorption • Helminthes infection Malignant diseases:Depression of appetite due to renal failureParasites: (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.