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Endocrine System
Study Guide, Endocrine 9-10
Pituitary Gland
 2 lobes
1. Anterior pituitary lobe (adenohypophysis)
Glandular tissue
 Releases hormones formed within pituitary

2. Posterior pituitary lobe (neurohypophysis)
 Glial-like supporting cells and nerve fibers
 Releases hormones formed within hypothalamus
Anterior Pituitary Hormones
• Growth hormone (GH)
• Thyroid stimulating hormone (TSH) Tropic
• Adrenocorticotropic hormone (ACTH) Tropic
• Follicle stimulating hormone (FSH) Tropic
• Luteinizing hormone (LH) Tropic
• Prolactin
• Melanocyte stimulating hormone (MSH)
Tropic = affects activity of other endocrine glands
Pro-opiomelanocortin (POMC)
 The “prohormone”
 A large precursor molecule of the anterior pituitary gland
 Enzymatic breakdown products include
 Adrenocorticotropic hormone (ACTH)
 Melanocyte-stimulating hormone (MSH)
 2 natural opiates = enkephalin & beta endorphin
From
POMC
Tropic
From
POMC
Tropic
Tropic
Anterior Pituitary Hormones
 Features
 All are proteins
 Utilize cAMP 2nd messenger system (except GH)
Anterior Pituitary Hormones
 Features cont.
 All are regulated by releasing or inhibiting factors made by the hypothalamus

Hypothalamic hormones travel through a delivery system to the anterior pituitary
o “Portal system”
Hypothalamus
Hypothalamic neuron
cell bodies
Superior
hypophyseal artery
Hypophyseal
portal system
• Primary capillary
plexus
• Hypophyseal
portal veins
• Secondary
capillary
plexus
Anterior lobe
of pituitary
TSH, FSH,
LH, ACTH,
GH, PRL, MSH
1 When appropriately
stimulated,
hypothalamic neurons
secrete releasing and
inhibiting hormones
into the primary
capillary plexus.
2 Hypothalamic hormones
travel through the portal
veins to the anterior pituitary
where they stimulate or
inhibit release of hormones
from the anterior pituitary.
3 Anterior pituitary
hormones are secreted
into the secondary
capillary plexus.
(b) Relationship between the anterior pituitary and the hypothalamus
Copyright © 2010 Pearson Education, Inc.
Figure 16.5b