Transcript Pituitary
Endocrine Physiology Pituitary 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 InsulinLike 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 postpituitary surgery Questions?