I
HORSESHOE KIDNEY
SOURCES AND EFFECTS OF PARTICULAR HORMONES
The various glands of the hormonal system constitute a
control and communications network that is complementary
to the nervous system. However, instead of using nerve
impulses, the glands secrete chemical messages (in the form
of hormones) to affect other glands and tissues in various
parts of the body. Hormones are carried in the bloodstream
to their targets, where they exert their specific effects. The
table below lists the hormones that are secreted by different
parts of the body and gives a description of their wide-
ranging actions.
Gland or hormone-
secreting tissue
Hormone secreted
Effects
Hypothalamus
Releasing or inhibiting hormones
Stimulate or suppress hormone secretion by pituitary gland
Pituitary gland
Growth hormone
Stimulates growth and metabolism
Prolactin
Stimulates milk production after childbirth
ACTH (adrenocorticotrophic hormone)
Stimulates hormone production byadrenal glands
TSH (thyroid-stimulating hormone)
Stimulates hormone production bythyroid gland
FSH (follicle-stimulating hormone);
LH (luteinizing hormone)
Stimulate gonads (ovaries or testes)
ADH (antidiuretic hormone)
Acts on kidneys to conserve water
Oxytocin
Stimulates contractions of uterus during labour and milk let-down
reflex in breast-feeding
MSH (melanocyte-stimulating hormone)
Acts on skin to promote production of skin pigment (melanin)
Brain
Endorphins; enkephalins
Alleviate pain; boost mood
Thyroid gland
Thyroid hormones
Increase metabolic rate; affect growth
Calcitonin
Lowers level of calcium in blood
Parathyroid glands
Parathyroid hormone
Increases level ofcalcium in blood
Thymus
Thymic hormone
Stimulates lymphocyte development
Heart
Atrial natriuretic factor
Lowers blood pressure
Adrenal glands
Adrenaline (epinephrine); noradrenaline (norepinephrine)
Prepare bodyfor physical and mental stress
Hydrocortisone
Affects metabolism
Aldosterone
Regulates sodium and potassium excretion by kidneys
Androgens
Affect growth and sex drive (in both males and females)
Kidneys
Renin
Regulates blood pressure
Erythropoietin
Stimulates production of red blood cells
Pancreas
Insulin
Lowers blood sugar level
Glucagon
Raises blood sugar level
Placenta
Chorionic gonadotrophin (HCG);
oestrogens; progesterone
Maintain pregnancy
Gastrointestinal tract
Gastrin; secretin; cholecystokinin
Regulate secretion ofsome digestive enzymes
Testes
Testosterone
Affects development of male secondary sexual characteristics and
genital organs
Ovaries
Oestrogens; progesterone
Affect development offemale secondary sexual characteristics
and genital organs; control menstrual cycle; maintain pregnancy
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