Endocrine Physiology Pituitary Bob Bing-You, MD, MEd, MBA Medical Director Maine Center for Endocrinology

Anterior Pituitary 1 cm diameter, 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 1 st 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?