Hypothalamic and Pituitary Hormones Flashcards
What is a negative regulator of GH?
Somatostatin
What is a negative regulator of prolactin?
Dopamine
The effects of GH are mediated through
IGF-1
Physiological Actions of GH in childhood
Promotes linear growth
Growth of long bones, cartilage, muscle, organ systems
Physiological Actions of GH in adulthood
Increases protein synthesis and bone density
Promotes lipolysis, inhibits lipogenesis
Promotes gluconeogenesis and glucose release
Opposes insulin-induced glucose uptake in adipose tissue, reduces insulin sensitivity
Features of GH deficiency in children
short stature
Adiposity
hypoglycemia
Features of GH deficiency in adults
increased generalized adiposity Decreases skeletal muscle mass decreased bone density Cardiac muscle atrophy Atherogenic blood lipid profile Fatigue, weakness, depression, malaise
synthetic GHRH
Sermorelin
Sermorelin (synthetic GHRH) indication
used if defective GHRH release but normally functioning anterior pituitary somatotrophs
Recombinant human GH
Somatropin
Somatrem
Recombinant IGF-1
Mecasermin
Mecasermin (recombinant IGF-1) indication
Used in children where IGF-1 deficiency is due to mutations of GH receptor: Laron dwarfism or Ab against GH
Somatropin formulation
191-amino acid peptide, identical to native hGH
Somatrem
192-amino acid peptide consistign of 191aa of GH plus extra methionine residue at N-terminus (for stability, less allergic response)
Recombinant hGH (somatropin, somatrem) MOA
replaces GH
Recombinant hGH (somatropin, somatrem) Indications
Documented growth failure in pediatric pts with: GH deficiency Chronic renal failure Prader-Willi syndrome Turner syndrome
SGA w/ failure to catch up by 2
Idiopathic short stature, non GH-deficient (>2.25 S.D. below mean height)
GH deficiency in adults
Wasting in AIDS pts
Short bowel syndrome
Recombinant hGH (somatropin, somatrem) efficacy in children
Increases linear growth
Weight gain
Increases muscle mass, organ size, RBCs
Recombinant hGH (somatropin, somatrem) efficacy in adults
Increases bone mineral density Decreased central adiposity Increases muscle mass Improves lipid profile Improves cardiac function Improves sense of well being
Recombinant hGH (somatropin, somatrem) side effects
Leukemia Rapid growth of melanocytic lesions Hypothyroidism (GH counteracts TSH) Insulin resistance Arthralgia Increase in cytochrome p450 activity
Recombinant hGH (somatropin, somatrem) contraindications
Ped pts with closed epiphyses Intracranial lesion Active malignancy Proliferative diabetic retinopathy Cautin in diabetes
What is the effect of glucocorticoids on somatropin
Inhibit growth-promoting effect
What is the most common cause of growth hormone excess
Benign anterior pituitary tumor
Growth hormone excess in children
Gigantism
Occurs before the closure of epiphyses because excess IGF1 causes excessive longitudinal bone growth
Growth hormone excess in adults
Acromegaly
Occurs after epiphyses close, IGF-1 promotes growth of deep organs and cartilaginous tissue
Characteristics of acromegaly
thickening of bone (face, hands)
Large facial structure
Macroglossia
Hepatomegaly
Standard treatment for larger pituitary adenoma
Transsphenoidal surgery to remove the tumor
Medical options for smaller adenomas
Somatostatin analogues
GH receptor antagonist
Dopamine receptor agonist
Somatostatin analogues
Octreotide
Lanreotide (Europe)
GH receptor antagonist
Pegvisomant
Dopamine receptor agonist
Bromocriptine
Octreotide
Synthetic long-lasting peptide analogue of somatostatin
Octreotide MOA
Inhibits GH secretion
Octreotide indication
Control pituitary adenoma growth in acromegalic patients
Carcinoid crisis (flushing, diarrhea)
Secretory diarrhea from VIPoma
To control acute GI bleeding
Octreotide Side Effects
Nausea, vomiting, abdominal cramps, GI discomfort
Cardiac effects
Hypoglycemia
Gallstones
Octreotide Therapeutic Considerations
Decreases cyclosporin levels
Increases the availability of bromocriptine
GH Receptor Antagonist
Pegvisomant
Pegvisomant structure
Recombinat protein of 191 aa with mutliple polyethylene glycol (PEG) residues -prolongs half life
Pegvisomant MOA
Normally GH binds 2 receptors, dimerizes > signal transduction. Pegvisomant does not bind to the 2nd receptor, blocks signal transfuction = competitive antagonist of GH
Decreases serum IGF-1
Pegvisomant Indications
Acromegaly that is refractory to other treatment
Pegvisomant side effects
Increased pituitary adenoma size
Elevated serum aminotransferase levels
Pegvisomant Therapeutic Considerations
Should have yearly MRI to exclude enlarging adenoma
Liver function tests periodically
What do the gonadotroph cells in the pituitary secrete in response to pulsatile GnRH?
LH and FSH
What is the function of FSH in women?
Ovarian follicle development
FSH stimulates conversion of androgens to estrogens in the granulosa cells
What is the function of LH in women?
Stimulates androgen production in the ovary (theca cells)
What is the function of FSH in men?
Regulates spermatogenesis
Produces androgen binding protein
What is the function of LH in men?
Stimulates production of testosterone by the Leydig cells
Gonadotropins
Human menopausal gonadotropins, menotropins
Human chorionic gonadotropin
Urofollitropin
Follitropin
Gonadotropin Releasing Hormone analogue (short half-life)
Gonadorelin
stimulatory-pulsatile form
Gonadotropin Releasing Hormone analogue (long half-life)
Goserelin, Histrelin, Leuprolide, Nafarelin, Triptorelin
inhibitory-continuous form
GnRH receptor antagonists
Ganirelix, Cetrorelix, Abarelix
Menotropins
Obtained from the urine of menopausal women
Contain FSH and LH
hCG
placental hormone and LH agonist
Urofollitropin
Purified FSH isolated from urine of postmenopausal women
Follitropin
Recombinant form of human FSH
Gonadotropin MOA
Replaces FSH and LH
Gonadotropin indications
Ovulation induction in women with anovulation (hypogonadotropic hypogonadism, PCOS, obesity)
Controlled ovarian hyperstimulation in IVF
Infertility in male hypogonadotropic hypogonadism
Gonadotropin Side Effects
Ovarian hyperstimulation syndrome Increase in multiple pregnancies Increased risk of gynecomastia Ovarian cancer Ovarian cysts and hypertrophy
Gonadotropin Contraindications
Any endocrine disorder other than anovulation
Primary gonadal failure
Pituitary tumor or sex-hormone dependent tumors
Ovarian cyst/enlargement
Pregnancy
Gonadorelin (synthetic GnRH, short acting) MOA
“Pulsatile GnRH secretion”
Stimulates gonadotroph cells to produce and release LH and FSH
Gonadorelin Indication
Mostly for diagnosis of hypogonadism
Stimulate ovulation
Infertility in men with hypothalamic hypogonadotropic hypogonadism
Gonadorelin Side Effects
Anaphylaxis
Lightheadedness, flushing
Hypersensitivity dermatitis
GnRH Agonist, Long acting
Goserelin, Histrelin, Leuprolide, Nadarelin, Triptorelin
GnRH Agonist, Long acting MOA
Sustained, nonpulsatile administration of GnRH inhibits the release of FSH and LH, desensitizes GnRH receptors
1st transient increase in gonadal hormone levels (flare), then long lasting suppression of gonadotropins and gonadal hormones
GnRH Agonist, Long acting, indication
Keep LH low in ovarian hyperstimulation for multiple mature oocytes for assisted repro tech (IVF)–> leuprolide, nafarelin
Endometriosis and uterine fibroids (leuprolide, nafarelin, goserelin)
Adjunct in prostate cancer (leupro, goserelin, histrelin, triptorelin)
Central precocious puberty (leupro, nafarelin)
Advancer breast and ovarian cancer, amenorrhea and infertility in women with PCOS
GnRH Agonist, Long acting, side effects
hot flashes, sweats, headache (lack of estrogen, menopause)
osteoporosis
urogenital atrophy
GnRH Agonist, Long acting, contraindications
Pregnancy
Breast feeding
GnRH receptor antagonists
Ganirelix, Cetrorelix, Abarelix
GnRH receptor antagonists MOA
Competitive antagonists of GnRH receptors
Inhibits secretion of FSH, LH
No flare effect
Ganirelix and Cetrorelix indications
Keeps LH low in controlled ovarian hyperstimulation for assisted repro tech (IVF)
Abarelix
Metastatic prostate cancer
GnRH receptor antagonists side effects
Ovarian hyperstimulation syndrome
QT interval prolongation (abarelix)
Ectopic pregnancy, thrombotic disorder, spontaneous abortion (ganirelix)
Anaphylaxis (cetrorelix)
Abarelix side effect
QT interval prolongation
Ganirelix side effects (3)
Ectopic pregnancy, thrombotic disorder, spontaneous abortion
Cetrorelix side effect
Anaphylaxis
GnRH receptor antagonists Contraindications
Pregnancy, lactation, ovarian cysts or enlargement (not due to PCOS)
Primary ovarian failure
Thyroid of adrenal dysfunction
Vaginal bleeding of unknown etiology
Which cells of the anterior pituitary produce and secrete prolactin?
Lactotrophs
Prolactin release is inhibited by ____
dopamine secreted by hypothalamus
Prolactin release is increased by
Thyrotropin-releasing hormone (TRH)
Is there any negative feedback regulation on prolaction?
no- does not stimulate hormone secretion in target organ (mammary gland)
What stimulates prolactin production during pregnancy?
Increasing estrogen levels
What effect does estrogen have on prolactin during pregnancy?
Increases production but antagonizes its action, preventing lactations until after parturition
What action is the powerful stimulus for prolactin release?
Suckling
Physiological actions of prolaction
Regulates mammary gland development, milk protein biosynthesis and secretion
Increased prolactin inhibits GnRH release (suppresses ovulation during lactation)
Causes of hyperprolactinemia
Rarely due to hypothalamic destruction
More commonly due to prolactin secreting adenomas
Hyperprolactinemia produces
Amenorrhea, galactorrhea, and infertility in women
Loss of libido and infertility in men
If large tumor > visual changes due to compression of the optic nerves
Dopamine Receptor Agonists
Bromocriptine, Cabergoline, Pergolide
Quinagolide (Europe)
Treatment of prolactin deficiency
No preparation of prolactin is available to treat these patients
Dopamine Receptor Agonists MOA
High affinity for dopamine D2 receptors
Inhibit pituitary prolactin release
Dopamine Receptor Agonists Indications
Amenorrhea, galactorrhea, infertility from hyperprolactinemia, premenstrual syndrome (Bromocriptine, Cabergoline)
Acromegaly (high doses, helpful only if tumor secretes prolactin and GH, use in combo with Octreotide (Bromocriptine)
Parkinson’s Disease (Bromocriptine, Pergolide, Cabergoline)
Dopamine Receptor Agonists Side Effects
Orthostatic hypotension
Cerebral vascular accident, seizure, acute MI (Bromo)
Arrhythmia, MI, heart failure (pergo)
Pulmonary fibrosis and pleural effusion (cabergo)
Bromocriptine side effects
Cerebral vascular accident, seizure, acute MI
Pergolide side effects
Arrhythmia, MI, heart failure
Cabergoline side effects
Pulmonary fibrosis and pleural effusion
Dopamine Receptor Agonists Contraindications
Hypersensitivity to ergot derivatives
Uncontrolled hypertension
Toxemia of pregnancy
Which of the 3 dopamine receptor agonists causes less nausea?
Cabergoline
How can you reduce nausea with the dopamine receptor agonists? What is the potential side effect?
Intravaginal administration
May cause local irritation
What are the effects of dopamine receptor agonists and alcohol?
Alcohol intolerance may occur
What is the concern with giving dopamine receptor agonists and a antihypertensive?
Coadministration can potentiate hypotension