1. Pituitary Gland & Hypothalamus

2. Hypothalamus and Pituitary Gland
The hypothalamus and pituitary gland work together to control other endocrine glands.
They are connected by the infundibulum.
The pituitary is composed of the:
Anterior pituitary (glandular)
Posterior pituitary (neural)
Alternative names:
Anterior pituitary: adenohypophysis, pars distalis, pars anterior
Posterior pituitary: neurohypophysis, pars nervosa
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3. Pars intermedia – separates anterior from posterior
PVN – paraventricular hypothalamic nucleus
SON – supraoptic hypothalamic nucleus

4. Pituitary Gland Master Gland
Controls growth & activity of the Thyroid Gland, Adrenal Gland, Gonads, & Liver
“Middleman” between the brain (CNS) and the peripheral endocrine organs
Pituitary hormones act on endocrine and non-endocrine tissue
Located outside the blood-brain barrier

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Pituitary Gland
Anterior lobe (adenohypophysis)
Comprises 75% of the weight of the pituitary gland
Secretes 7 hormones.
Posterior lobe (neurohypophysis)
Made of neural tissue
Releases two hormones/neuropeptides made by the hypothalamus.
Oxytocin
Vasopressin/ADH
Hormone secreting cells of the neurohypophysis (posterior pituitary), the adrenal medulla and the pineal gland are regulated by direct neural innervation.
Stimulation of hormone secretion by nerves is referred to as neuroendocrine transduction.
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6. Hypothalamus
Secretes releasing and inhibiting hormones that control the release of hormones by the pituitary gland.
They reach the pituitary gland via the hypophyseal portal system.

7. Hypophysiotropic Hormones
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8. Hypophyseal Portal System
Hypophyseal arteries come off of the carotid artery
The arteries of the pituitary gland arise from the internal carotid arteries as the inferior and superior hypophyseal arteries. The inferior hypophyseal arteries mainly supply the pars nervosa before forming short portal vessels to supply the pars distalis. The superior hypophyseal arteries supply the floor of the hypothalamus, the median eminence. The capillary plexus formed by the superior hypophyseal artery in the median eminence form into long portal vessels which run down in the pituitary stalk to form a capillary plexus in the pars distalis. In the median eminence the capillary plexus receives secretions from releasing factor cells.
The blood is drained from the pituitary by inferior hypophyseal veins into the dural venous sinuses.
Coming from carotid
Superior – anterior pituitary
Inferior – posterior pituitary
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9. Anterior Pituitary - Trophic Hormones
Human Growth Hormone - hGH
Thyroid-Stimulating Hormone - TSH
Follicle-Stimulating Hormone - FSH
Luteinizing Hormone - LH
Prolactin - PRL
Adrenocorticotropic Hormone - ACTH
Melanocyte-Stimulating Hormone - MSH
Trophic- “nourishing”

10. Human Growth Hormone (hGH/GH)
a.k.a. Somatotropin
Most abundant AP hormone
Produced by somatotrophs
Account for majority of cells present in AP
1° - acts on liver (IGF)
GHRH stimulates; SST/GHIH inhibits
Somatostatin (SST)
Growth Hormone Releasing Hormone (GHRH)
SST: decreases GH secretion at AP and by decreasing GHRH
If you have high IGF-I it will feedback to increase SST and then decrease GH and GHRH

11. Long Loop Feedback – target tissue secretes hormone that affect the pituitary and the hypothalamus
Short Loop Feedback– pituitary (hypophyseal) hormone feeds back to the hypothalamus to shut it down
Ultrashort Feedback – Hormone released from the pituitary shuts itself off.

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hGH Feedback Loops
growth hormone-releasing hormone (GHRH) and growth hormone-inhibiting hormone (GHIH).
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

13. Thyroid-Stimulating Hormone (TSH)
a.k.a. Thyrotopin
Produced by thyrotrophs
1°- acts on thyroid (T3/T4).
In mammals  thermogenesis
Stimulated by TRH

14. Follicle-Stimulating Hormone (FSH)
a.k.a Follitropin
Produced by gonadotrophs
Specifically, FSH-gonadotroph
1°- in men: promotes spematogenesis;
in women: follicular growth (estrogen/progesterone)
Stimulated by GnRH
Increases LH receptors in Leydig cells (sperm production)

15. Luteinizing Hormone (LH)
a.k.a. Lutropin
Produced by gonadotrophs
Specifically, LH-gonadotroph
1° - in men: acts on testes (testosterone);
in women: acts on ovaries (ovulation/CL)
Stimulated by GnRH
Corpus lutem

16. Prolactin (PRL) Produced by lactotrophs
A.k.a. mammotrophs
PRL increases during pregnancy and reaches maximal values at parturition
Milk production in post-partum women
Stimulated by nursing infant
Prolactin-inhibiting factor- a.k.a. dopamine via tonic inhibition

17. Adrenocorticotropic Hormone (ACTH)
a.k.a. Corticotropin
Produced by corticotrophs
1° action- stimulates steroid biosynthesis within the adrenal cortex; cortisol
Stimulated by CRH
High cortisol = Cushings Disease
Low cortisol = Addisons Disease
Primary Cushings- high cortisol/ Secondary Cushings – high ACTH
Primary Addisons- low cortisol / Secondary Addisons- low ACTH
Cushings Disease
Excessive secretion of ACTH
Characterized by excess cortisol and alterations of glucose metabolism
Hyperpigmentation, wasting of muscle, puffiness (water retention)
Pituitary or hypothalamus tumor
Addison’s Disease
Absence of ACTH secretion
Characterized by decreased cortisol secretion

18. Melanocyte-Stimulating Hormone (MSH)
a.k.a. Melanotropin
Produced by corticotrophs
Disperse melanin pigment in melanocytes in the skin
Not secreted in large amounts by AP

19. Credit: Dr. Michael Ormsbee, Florida State University

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Hypothalamus and A.P.
Negative feedback loops control the secretions of:
Thyrotrophs
TSH
Gonadotrophs
LH, FSH
Corticotrophs
ACTH, MSH
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

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Posterior Pituitary
The posterior pituitary gland does not synthesize any hormones.
It stores and releases from axon terminals two hormones:
oxytocin (OT)
anti-diuretic hormone (ADH)/vasopressin
Axons from the neurosecretory cells form the hypothalamohypophyseal tract.
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

22. Hypothalamus and Post. Pituitary
The PP contains only neuronal axonal endings.
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23. Posterior Pituitary - ADH
Antidiuretic hormone (ADH)/vasopressin
Amount secreted varies with blood osmotic pressure.
Its function is to decrease urine output.
Osmoreceptors (neurons) in the hypothalamus monitor blood osmotic pressure.
↑ blood volume causes ↓ ADH secretion
↓ blood volume causes ↑ ADH secretion
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ADH Feedback Loop
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

25. Posterior Pituitary - Oxytocin
The “cuddle” or “love” hormone
Active during parturition and post-partum
Stretching of cervix = ↑↑ oxytocin release
Results in ↑ smooth muscle contractions of uterus
After birth – responsible for milk let-down/ejection
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.