Endocrine Physiology
Pituitary
Bob Bing-You, MD, MEd, MBA
Medical Director
Maine Center for Endocrinology
Anterior Pituitary
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1 cm diameter, 0.5-1 gm weight
Sits in sella turcica
Connected with hypothalamus via stalk
The “master gland”
Six major hormones
Which is not an anterior pituitary
hormone?
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A. Prolactin
B. ACTH
C. Luteinizing hormone
D. Vasopressin
E. Thyrotropin
Growth Hormone
• Promotes growth as child
• Facilitates protein formation, via InsulinLike Growth Factor 1
• Deficiency = short stature as child
• As adult: poor Quality of Life, osteoporosis,
hyperlipidemia
• Excess = acromegaly
IGF-1
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Produced in liver predominantly
Paracrine effects
Receptors important for function
IGF-1 approved as therapy
Adrenocorticotropin
• Stimulated by corticotropin-releasing
hormone [CRH]
• Under negative feedback control by cortisol
• Stimulates adrenal cortex to produce
glucocorticoids such as cortisol
Thyrotropin [TSH]
• Stimulated by thyrotropin-releasing
hormone [TRH]
• Under negative feedback control by T4 and
T3
• Stimulates thyroid to increase iodine
uptake, produce thyroid hormone
FSH/LH
• Stimulated by gonadotropin-releasing
hormone [GnRH]
• Under negative feedback by gonadal
steroids [estrogen and testosterone]
• FSH promotes follicle or sperm
development
• LH promotes estrogen or testosterone
production
Disease deficiency states
• Non-functioning tumors
– FSH/LH often first to go
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Head trauma
Infiltrative diseases
“Empty sella” syndrome
Rx underlying cause; replace end hormonal
product
Disease excess states
• Acromegaly – rare
• Cushing’s Disease – rare; tumor producing
ACTH
• TSH producing tumor – rarer, usually
associated with GH - tumor
She has:
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A. Prolactinoma
B. Cushings Syndrome
C. Hangover
D. Hypothyroidism
E. Acromegaly
Prolactinomas
• Most common secretory pituitary tumor
• 40% of all pituitary tumors
• Most common symptom = hypogonadism
– Amenorrhea/galactorrhea
– Low libido, erectile dysfunction, gynecomastia
• PRL level and MRI for diagnosis
• Medical Rx almost always 1st choice
Medical Therapy
• Tonically inhibitory dopaminergic fibers
from hypothalamus
• Bromocriptine [Parlodel], cabergoline
[Dostinex], quinagolide, pergolide
• All effective in reducing tumor size and/or
PRL
• ~25% of treated patients have <25% to no
decrease size
Bromocriptine vs. cabergoline
• Bromocriptine
– Since 1960’s
– Nausea,
lightheadedness
– Daily
– 2.5 mg – 10 mg/day
• Cabergoline
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Newest
Once a week
Little side effects
0.5 – 2.0 mg/week
• Both safe in
pregnancy
Take-home Points
• Anterior pituitary major player in normal
endocrine physiology
• Excess states are surgical problems except
for prolactinomas
Questions?
Which is not true?
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A. Too much IGF-1 will cause acromegaly
B. FSH surge causes ovulation
C. Most prolactinomas are medically treated
D. Sarcoidosis can cause adrenal
insufficiency
Posterior Pituitary
• Antidiuretic hormone [ADH] aka
“vasopressin”
• Formed in supraoptic nuclei in
hypothalamus; accumulate in nerve endings
in pituitary
• Without ADH, renal collecting tubules
totally impermeable to water
ADH
• Minute quantities ADH can cause water
reabsorption
• ADH binds to receptors, triggers cAMP,
open pores to water
• Under regulation osmoreceptors, sense
concentration in extracellular fluid
Diabetes insipidus
• Nephrogenic: renal resistance to ADH
– E.g., lithium
• Central D.I.: decreased posterior pituitary
secretion of ADH
Diagnosis of Diabetes Insipidus
must include:
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A. Copious urine excretion [500 cc/hr]
B. Low urine specific gravity [e.g., < 1.005]
C. Hypernatremia
D. Hypokalemia
Clinical Vignette
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64 y.o. woman post-op CABG
Vasopression drip
Stopping drip, BP drops, Na climbs to 154
Daughter states mother drinking gallons
daily for few years
Treatment of D.I.
• Maintain access to free water
• D5W IV
• DDAVP [desmopressin]
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Nasal, oral, IM or IV
Can be given once or twice/day
Resistance rare
Toxic effect is hyponatremia
Key Points
• ADH major hormone of posterior pituitary
• Diabetes insipidus more likely seen postpituitary surgery
Questions?