Endocrine Structure Primary Hormones
HYPOTHALAMUS dopamine
(continued) GONADOTROPIN-RELEASING HORMONE
(GNRH)
GROWTH HORMONE-RELEASING
HORMONE(GHRH)
OXYTOCIN
somatostatin
THYROTROPIN-RELEASING HORMONE
(TRH)
ISLETS OF LANGERHANS GLUCAGON
INSULIN
somatostatin
KIDNEYS ERYTHROPOIETIN(EPO)
RENIN
ovaries ESTROGENS
INHIBIN
PROGESTERONE
PARATHYROID GLANDS PARATHYROID HORMONE
PINEAL GLAND MELATONIN
PITUITARY GLAND
anterior pituitary lobe ADRENOCORTICOTROPIN HORMONE
(ACTH)
FOLLICLE-STIMULATING HORMONE(FSH)
GROWTH HORMONE(GH)
LUTEINIZING HORMONE(LH)
PROLACTIN
THYROID-STIMULATING HORMONE(TSH)
posterior pituitary lobe stores and releases as needed:
ADH
oxytocin
PLACENTA CHORIONIC GONADOTROPIN
estrogen
prolactin
human placental lactogen (hPL)
progesterone
RELAXIN
testes inhibin
TESTOSTERONE
THYMUS THYMOSIN
Endocrine Structure Primary Hormones
THYROID GLAND CALCITONIN
THYROXINE(T 4 )
TRIIODOTHYRONINE(T 3 )Bridge between control systems: the hypothala-
mus The HYPOTHALAMUSis the structural and func-
tional bridge between the BRAINand the endocrine
system. Composed primarily of brain tissue, it
receives a constant barrage of NERVEsignals from
the thalamus, a structure of the brain that serves
as a neurologic switchboard for sensory informa-
tion related to sight, sound, touch, and taste. The
physical transition from thalamus to hypothala-
mus is difficult to distinguish, highlighting the
blurred line between neurologic and endocrine
activity that gives rise to the subspecialty of medi-
cine known as neuroendocrinology.
The functions of the hypothalamus primarily
relate to survival. Through a combination of nerve
impulses and hormonal signals, the hypothalamus
regulates BLOOD PRESSURE, HEART RATE, gastrointesti-
nal activity and digestion, body temperature,
hunger, and thirst. Hypothalamic hormones target
the PITUITARY GLAND, acting either to stimulate or
inhibit (stop) the pituitary’s secretions. The hypo-
thalamus receives hormonal messages directly
from the pituitary gland and indirectly through
HORMONElevels in the BLOOD, one of a number of
feedback mechanisms that helps regulate the
hypothalamus’s hormonal activity and maintain
hormonal balance within the body.
Hormonal choreography: the pituitary gland
Extending downward from the base of the hypo-
thalamus, the pituitary gland bulbs out from the
end of a short stalk. A dedicated capillary net-
work, the hypophyseoportal circulation, circulates
blood between the hypothalamus and the pitu-
itary gland to fast track hormone delivery from
the hypothalamus to the pituitary gland. A sepa-
rate network of blood vessels supplies each struc-
ture with blood from the body’s circulation to
meet the metabolic needs of its cells and to carry
pituitary hormones into the body. Communication
between the pituitary gland and the hypothala-
mus is by necessity intimate and continuous, as
the relationship between these two structures reg-
ulates basic bodily functions of survival.98 The Endocrine System