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My DEMS 4 > Hypothalamic Pituitary Pharmacology > Flashcards

Hypothalamic Pituitary Pharmacology Flashcards

1
Q

Anterior pituitary hormone release

A
  • hypothalamic hormone release under CNS control via NTs
  • release of anterior pituitary hormones controlled by hypothalamic hormones
  • released from neruons to portal circ to pituitary to systemic circ to act on endocrine glands

(Posterior pit release: synth in hypothal, transport to neruonal terminal in posterior pit, released into circ and act on target tissue directly)

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2
Q

Growth hormone (pharm name/info)

A
  • Somatropin
  • t1/2 25 mins, peak levels in 2-4 hours, active level persist 36 hours
  • can be given SC or IM
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3
Q

Release of GH increased by, decreased by

A

increased by exercise, hypoglycemia, dopamine, L-DOPA, arginine, Ghrelin
-release decreased by somatostatin and decreased by dopamine agonists in acromegaly

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4
Q

Does GH work directly or indirectly?

A
  • Indirectly
  • Stimulates synthesis of IGF-1 in growth plate cartilage and liver– linear and skeletal muscle growth
  • Produces anabolic and metabolic effects: positive nitrogen balance, increased lipolysis, increased FFA and glucose
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5
Q

GH uses

A

-Replacement therapy in children with deficiency:
given daily at bedtime, SC, or 3x/wk IM
-If GH insensitive (Laron Dwarf), can treat with recombinant IGF-1 (mecasermin), concern w/ hypoglycemia
-Use in idiopathic short stature in kids controversial
-Treatment of poor growth due to Turner’s syndrome, Prader-Willi syndrome, and chronic renal insufficiency
-GH deficiency in adults (most commonly due to pituitary tumor or consequences of its treatment - surgery and/or radiation)
-wasting or cachexia in AIDS patients
-Patients with short bowel syndrome dependent on total parenteral nutrition

Illicit:

  • use by athletes to increase muscle mass and improve performance despite lack of controlled studies
  • use by healthy elderly for anti-aging effects: small changes in body composition and increased rates of adverse events
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6
Q

SE of GH

A
  • generally safe in kids
  • nsulin resistance and glucose intolerance may occur
  • Slight increased risk for idiopathic intracranial hypertension (pseudotumor cerebri)
  • Rarely pancreatitis, gynecomastia, nevus growth
  • Misuse in athletes: Acromegaly, arthropathy, visceromegaly, extremity enlargement
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7
Q

Off label use of hGH is…

A

illegal!

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8
Q

GHRH pharmacokinetics

A

IV, intranasal, SC
-Adverse effects: rare, facial flushing (IV), antibody formation with continue use
-Rapidly stimulates GH synthesis and secretion
-Binds to GPCR coupled to Gs, increasing cAMP and Ca2+ levels in somatotrophs
-Ghrelin also stimulates GH release via different GPCR:
secreted by endocrine cells in stomach
stimulates appetite and increased food intake

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9
Q

GHRH uses

A
  • diagnostic evaluation of patients with idiopathic GH deficiency
  • potential use in GH deficiency children, potentially fewer SE
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10
Q

Tesamorelin

A

GHRH analog available for use in HIV patients with lipodystrophy secondary to use of highly active retroviral therapy (HAART), reduces excess abdominal fat

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11
Q

Somatostatin

A
  • aka SST, Growth Hormone inhibiting Hormone, Somatotropin Release-inhibiting factor
  • present in hypothalamus, NS, gut, endocrine and exocrine glands– function varies
  • Inhibits GH release via GPCR coupled to Gi decreasing cAMP and K+ channels
  • Decreases secretion of gastric enzymes and acid- decreased GI motility- suppresses release of serotonin and gastroenteropancreatic peptides
  • reduces insulin and glucagon release, complex effects on blood glucose
  • interferes with TRH ability to release TSH
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12
Q

Somatostatin and analogs

A

somatostatin:
t1/2 3-4 min limiting therapeutic utility

octeotride: t1/2 90 min (duration 12 hrs); given SC every 6-12 hrs

octeotride (Sandostatin LAR depot) given IM every 4 weeks

Lanreotide: given SQ every 4 weeks

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13
Q

Uses of somatostatin analogs

A

Pituitary: excess growth hormone
Acromegaly (adults) and giagntism (kids)
-surgical resection preferred unless adenoma does not appear fully resectable, patient has high surgery risk, or does not choose surgery
-Long-acting somatostatin analog is preferred pharmacotherapy- utilized after response seen to SC octeotride
-Dopamine agonists may inhibit GH secretion in some pts, but not as effective as SST analogs

Nonpituitary:
Control of bleeding from esophageal varices and GI hemorrhage (constrict splanchnic arterioles)
-Carcinoid tumors, VIP secreting tumors
-Symptoms of WDHA syndrome (watery diarrhea, hypokalemia, achlorhydria)

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14
Q

Cabergoline

A

-preferred agent for adjuvant management of acromegaly with advantage of oral administration

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15
Q

Pegvisomant

A

GH receptor antagonist

-single daily dose, SC

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16
Q

SE of somatostatin analogs

A
  • transient detrioration in glucose tolerance (hyperglycemia)
  • abdominal cramps
  • loose stools
  • Cardiac effects: sinus bradycardia and conduction disturbances
17
Q

Prolactin release and actions

A
  • under inhibitory control by hypothalamic dopamine at D2 receptors
  • main stim for release is suckling
  • Stimulates milk production if appropriate levels of insulin, estrogens, progestins, and corticosteroids are present
  • Stimulates proliferation and differentiation of mammary tissue during pregnancy
  • Inhibits gonadotropin (FSH/LH) release and/or ovarian response to these hormones - related to lack of ovulation during breastfeeding
18
Q

Uses of Prolactin

A

-hypoprolactinemia: no preparation available for prolactin deficiency
-Hyperprolactinemia (prolactinomas):
dopamine agonists decrease secretion and reduce tumor size. All available as oral preparations: Bromocriptine
Cabergoline

19
Q

Bromocriptine

A
  • ergot derivative, activates D1 receptors

- frequent side effects include, n/v, HA, postural hypotension, less freq: psychosis, insomnia

20
Q

Cabergoline

A
  • preferred agent for hyperprolactinemia
  • more selective for D2 receptor and more effective in reducing prolactin secretion
  • better tolerated, less nausea, may cause hypotension and dizziness.
  • Concern with higher doses and valvular heart disease (agonist action at 5HT2b receptors)
21
Q

Vasopressin

A

“ADH”

  • parenteral admin
  • t1/2 20 mins
22
Q

Desmopressin

A

ADH analog that is more stable to degradation.

t1/2 1.5-2.5 hrs

23
Q

Pharmacodynamics of vasopressin

A
  • control of water content (distal nephrone and collecting tubules)
  • Released from supraoptic nuclei of hypothalamus (stim? rising blood osmolality, decrease in circ blood volume, release inhibited by alcohol)

Renal actions:

  • mediated by V2 receptors (GPCR coupled to Gs)
  • increase rate of insertion of water channels into luminal membrane, increase water perm, antidiuretic effect.
  • activates urea transporters, increase Na transport in distal nephron.
  • Non-renal V2 actions include release of coagulation factor VIII and von Willebrand’s factor.
24
Q

ADH actions at V1 receptors

A
  • GPCR (Gq)
  • vasoconstriction at vascular smooth muscle
  • BUT pressor responses occur in vivo only at much higher concentrations than those that produce maximal antidiuresis
25
Q

Cerebral diabetes insipidus and tx

A
  • post pit disease
  • head injury, pit tumor, cerebral aneurysm or ischemia; inadequate ADH secretion
Tx: desmopressin
nasally 1-2/d
ADR: nasal irritation
orally 2-3/d
ADRs: HA, nausea, cramps, allergic rxn, water intoxication

Tx Chlorpropamide (1st gen sulfonylurea)

  • potentiates action of small or residual amounts of ADH
  • option if intolerant to desmopressin
26
Q

Nephrogenic DI

A

-inadequate ADH actions
Congenital: diverse receptor and aquaporin mutations are known
Drug-induced:
lithium: reduces V2 receptor mediated stim of adenylyl cyclase.
Demeclocyline

Tx:
-low salt, low protein diet
-Thiazide diuretics: paradoxically reduce polyuria of pts with DI
NSAIDs: inhibit PG synthesis because PGs attenuate ADH induced antidiuresis, indomethacin has greatest efficacy

27
Q

SIADH

A

-syndrome of inappropriate secretion of ADH.
-incomplete suppression of ADH secretion under hypoosmolar conditions
Drugs most commonly implicated:
-Psychotropic agents: SSRIs, haloperidol, TCAD
-sulfonylureas (chlorpropamide)
-Vinca alkaloids chemo
-Methylenedioxy methamphetamine (MDMA)

Tx of hyponatremia:
-restrict free water intake
-Demeclocyline: inhibits ADH effects on distal tubule
-V2 receptor antagonist: Tolyaptan (costly, increases thirst)
Coniyaptan: IV (hospitalized SIADH pts)
WARNING: do not correct hyponatremia too rapidly: cerebellar pontine myelinolysis

28
Q

V1 receptor-mediated uses

A
  • Vasopressin
  • attenuates pressure and bleeding in esophageal varices via vasoconstriction of splanchnic arterioles (octeotride preferrred)
  • Used as a vasopressor for tx of pts with severe septic shock
  • alternative to epi in ACLS for shock refractory ventricular tachycardia/fibrillation
29
Q

V2 receptor mediated uses

A
  • option in nocturnal enuresis- oral desmopressin

- Von Willebrand’s disease (elevated vWF) and moderate hemophilia A (elevates factor VIII) -IV desmopressin

My DEMS 4 (23 decks)

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