MPBP 301: ENDOCRINOLOGYHYPOTHALAMUS / PITUITARY

IMAGING MODULE: Head & Neck I

= PITUITARY

= HYPOTHALAMUS

MRI

OBJECTIVES: HYPOTHALAMUS / PITUITARY

Describe the embryologic origins of the neuro- and adenohypophysis.

Describe the location of the pituitary and some of the clinical implications of that location.

Define the hormone products of the hypothalamus and list their target(s).

Define the hormone products of the neurohypophysis and list their targets.

Define the hormone products of the adenohypophysis and list their targets.

Draw and identify the key components of the control system for endocrine systems regulated through the adenohypophysis.

Describe the role of releasing hormones in control of hypothalamic-adenohypophyseal feedback systems.

Describe the role of tropic hormones in control of hypothalamic-adenohypophyseal feedback systems.

Describe the mechanism by which circulating hormones exert their negative feedback effect on the adenohypophysis.

(WHEATER)

EMBRYOLOGY INSTRUCTS

X-RAY

IMAGING MODULE: Head & Neck I

MRI

MRI

NERVESBLOOD

NEUROHYPOPHYSIS

AntiDiuretic Hormone (ADH) / Vasopressin

Oxytocin

GROWTH HORMONETHYROID HORMONECORTISOL(REPRODUCTIVE SYSTEM)

ADENOHYPOPHYSIS

RELEASINGHORMONES

TROPHICHORMONES

HYPOTHALAMIC – PITUITARYREGULATION: ADENOHYPOPHYSIS

SETPOINT:CNS / HYPOTHALAMUS

FEEDBACK:PITUITARY

THE KEY ELEMENTS(What you need to know)

Chromophils of the Anterior Pituitary

• Acidophils:• Somatotrophs: Growth Hormone• Lactotrophs Prolactin• Basophils: • Gonadotrophs: Follicle Stimulating

hormone, LH• Thyrotrophs: TSH• Corticotrophs: ACTH

Somatotrophs are the major cell type 50%; Lactotrophs, 20%; Gonadotrophs, 5%; Thyrotrophs 5%, Corticotrophs, 20%

THE TROPICHORMONES

THE RELEASING HORMONES

TRH in the PV NUCLEUS

RELEASING HORMONES ARENOT MONOSPECIFIC*

TRH causes Prolactin ReleaseGnRH is same for FSH and LHGHRIH (ST) inhibits TSH releaseGHRIH (ST) regulates endocrine pancreasCRH regulates parturition

*Know Concept not facts

CNS REGULATION

THE SAME NEUROTRANSMITTERSAS ELSEWHERE IN THE CNS

COMPLICATES USE OF NEUROTRANSMITTERSTHERAPUTICALLY

WHAT ELSE DO RELEASING HORMONES DO?

MANY THINGS:

OVERALL CNS FUNCTION: BEHAVIORGASTROINTESTINAL SYSTEMENDOCRINE PANCREASPARTURITIONETC.

CONCEPT: I WILL NOT ASK

FEEDBACK ON PITUITARYREGULATION OF RH RECEPTORS

KEY CONCEPT

RTRH

TRH

PITUITARY FEEDBACK: NORMAL vs HIGH FEEDBACK

TSH

TRH TRH

RTRH

TRH TRH TRH

RTRH RTRH

+ + + +

T3 T3

__AP Cell AP Cell

TSH

NORMAL ELEVATED T3

TRHTRH

TRHTRH

TRH = Thyrotrophic Releasing HormoneTSH = Thyroid Stimulating HormoneT3 = Thyroid Hormone

RTRH RTRH

++

PITUITARY FEEDBACK: NORMAL vs HIGH FEEDBACK

TRH = Thyrotrophic Releasing HormoneTSH = Thyroid Stimulating HormoneT3 = Thyroid Hormone

RTRH

TRH

TSH

TRH TRH

RTRH RTRH

+ + +

T3

_AP Cell

ELEVATED T3

TRHTRH

RTRH RTRH

RTRH

TRH

TSH

TRH TRH

RTRH RTRH

+ + +

T3

_AP Cell

NORMAL

TRHTRH

RTRH RTRH

+ +

FIRST: T3ELEVATED

RTRH

TRHPITUITARY FEEDBACK: NORMAL vs HIGH FEEDBACK

TSH

TRH TRH

RTRH

TRH TRH TRH

RTRH RTRH

+ + + +

T3 T3

__AP Cell AP Cell

NORMAL ELEVATED T3

TRHTRH

TRHTRH

TRH = Thyrotrophic Releasing HormoneTSH = Thyroid Stimulating HormoneT3 = Thyroid Hormone

RTRH RTRH

TSH

++

SECOND: LOSS OFTRH RECEPTORS

RTRH

TRHPITUITARY FEEDBACK: NORMAL vs HIGH FEEDBACK

TSH

TRH TRH

RTRH

TRH TRH TRH

RTRH RTRH

+ + + +

T3 T3

__AP Cell AP Cell

TSH

NORMAL ELEVATED T3

TRHTRH

TRHTRH

TRH = Thyrotrophic Releasing HormoneTSH = Thyroid Stimulating HormoneT3 = Thyroid Hormone

RTRH RTRH

++

THIRD: TSH SIGNALREDUCED

RTRH

TRHPITUITARY FEEDBACK: NORMAL vs HIGH FEEDBACK

TSH

TRH TRH

RTRH

TRH TRH TRH

RTRH RTRH

+ + + +

T3 T3

__AP Cell AP Cell

TSH

NORMAL ELEVATED T3

TRHTRH

TRHTRH

TRH = Thyrotrophic Releasing HormoneTSH = Thyroid Stimulating HormoneT3 = Thyroid Hormone

RTRH RTRH

+_

FOURTH: THYROIDSHUTS DOWN

RTRH

TRH

TSH

TRH TRH

RTRH

TRH TRH TRH

RTRH RTRH

+ + + +

T3T3

__AP Cell AP Cell

TSH

NORMAL REDUCED T3

RTRH

RTRH

RTRH

RTRH

TRH TRH

TRHTRH

RTRH

RTRH

RTRH

RTRH

++

++

TRH = Thyrotrophic Releasing HormoneTSH = Thyroid Stimulating HormoneT3 = Thyroid Hormone

PITUITARY FEEDBACK: NORMAL vs LOW FEEDBACK

++

A CRITICAL FUNCTION TEST

A LOOK AHEAD

THYROID FEEDBACK MODULE

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