Endocrine Physiology Pituitary Bob Bing-You, MD, MEd, MBA Medical Director Maine Center for...
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Transcript of Endocrine Physiology Pituitary Bob Bing-You, MD, MEd, MBA Medical Director Maine Center for...
Endocrine PhysiologyPituitary
Bob Bing-You, MD, MEd, MBA
Medical Director
Maine Center for Endocrinology
Anterior Pituitary
• 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?
• A. Prolactin
• B. ACTH
• C. Luteinizing hormone
• D. Vasopressin
• E. Thyrotropin
Growth Hormone
• Promotes growth as child
• Facilitates protein formation, via Insulin-Like Growth Factor 1
• Deficiency = short stature as child
• As adult: poor Quality of Life, osteoporosis, hyperlipidemia
• Excess = acromegaly
IGF-1
• 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
• 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:
• 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– 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?
• 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:
• A. Copious urine excretion [500 cc/hr]
• B. Low urine specific gravity [e.g., < 1.005]
• C. Hypernatremia
• D. Hypokalemia
Clinical Vignette
• 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]– 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 post-pituitary surgery
Questions?