BMS2: The Endocrine System

Hypothalamic Releasing Hormones

Corticotropin RH, Gonadotropin RH, Thyrotropin, GHRH, Prolactin RH

What does corticotropin stimulate the release of

ACTH

What does gonadotropin stimulate the release of

LH and FSH

What does thyrotropin stimulate the release of

TSH

Hypothalamic Inhibiting Hormones

somatostatin, dopamin, prolactin inhibiting hormone

What does somatostatin inhibit

release of GH

What does dopamine inhibit

release of prolactin

What does substance P inhibit

synthesis and release of ACTH

What does substance P stimulate

secretion of GH, FSH, LH, prolactin

What is a major target of hypothalamic hormones

anterior pituitary

Anterior pituitary

adenohypophysis

What is the anterior pituitary derived from

embryonic ectoderm

How many types of epithelial cells does the anterior pituitary have

5 cell types, 5 hormones

How do hormones from the thalamus reach the anterior pituitary

via hypophyseal portal blood

Posterior pituitary

neurohypophysis

What is the posterior pituitary derived from

neural in origin, connected to hypothalamus via nerve tract

How do hormones from the hypothalamus reach the posterior pituitary

via axons of neurons

Anterior pituitary hormones

TSH, ACTH, GH, prolactin, FSH, LH

TSH effect

synthesis and secretion of T3, T4 from thyroid

What inhibits TSH

T4, T3

ACTH effect

synthesis and secretion of adrenocortical hormones

What inhibits ACTH

cortisol (adrenocortical hormone)

Growth hormone effect

decreased glucose uptake, increased (growth, protein synthesis, organ size, lean body mass, IGF liver production)

What inhibits GH

somatostatin, somatomedins, obesity, pregnancy, hyperglycemia, alcohol

What stimulates GH

deep sleep, exercise, GHRH, puberty, hypoglycemia, estrogen, stress, fasting, endogenous opiates

Prolactin effect

milk production and secretion, breast development, ovulation inhibition

What inhibits prolactin

dopamine, tonic inhibition

FSH effect

growth of follicles and estrogen secretion, maturation of sperm

What inhibits FSH

constant GnRH release

LH effect

ovulation, corpus luteum, synthesis of estrogen and progesterone, synthesis and secretion of testosterone

What inhibits LH

constant GnRH release, testosterone, progesterone

GH (somatotropin) function on bones

linear growth of bones in children, bone thickening in adults

GH (somatotropin) function on muscle

protein synthesis and muscle hypertrophy

What is used as fuel for GH action

Lipolysis, glycolysis, gluconeogenesis

When are GH levels highest

during sleep, fasting, or puberty

What increases GH

amino acids

How is GH released

in a pulsatile manner

What does GH do to adipose tissue

cause increase in free fatty acids through lipolysis, inhibits further GH release

What does GH do to the liver

cause increase in IGF-1 and glucose through glycolysis/gluconeogenesis, inhibits further GH release

What does GH do to the stomach

cause increase in ghrelin, stimulates further GH release

Increase in GH before closure of epiphyses

gigantism

Increase in GH after closure of epiphyses

acromegaly

Decrease in GH in children

dwarfism

What is common in acromegaly/gigantism

macroglossia, prognathism, carpal tunnel, DM, hypertension

Acromegaly manifestations

prominence (forehead, chin and jaw) enlargement (nose, lips, hands, and tongue)

Acromegaly and gigantism diagnosis

5x increase in IGF-1, glucose suppression test

Acromegaly and gigantism treatment

surgery, radiation therapy, somatostatin analogs/GH receptor antagonists

Acromegaly and gigantism dental manifestations

root hypercementosis, class III malocclusion, macroglossia, spaced out mandibular teeth

Dwarfism clinical manifestations

short height, large head, saddle nose, prominent forehead, delayed skeletal manifestation

Reduced muscle mass/strength, bone mass/osteoporosis, reduced energy levels, impaired concentration, increased body fat, lipid abnormalities

GH deficiency in adults

Dental manifestation of GH deficiencies

delayed eruption, hypodontia, crowding/malocclusion, retarded growth of mandible

Lack of FSH and LH

loss of secondary sex characteristics

Excess FSH and LH

menstrual irregularities, decreased libido, decreased secondary sex characteristics

Prolactin action

induces milk production during pregnancy and lactation, immune stimulatory effects, modulates inflammatory response

Stimulators of prolactin

vasoactive intestinal polypeptide, serotonin, growth factors, stimulation of nipples

Causes of hyperprolactinemia/hypersecretion of prolactin

prolactinoma (pituitary tumor), renal failure, PCOS, breast stimulation, stress of venipuncture, hypothyroidism, dopamine blockers

Pathophysiology of prolactinoma

compression of optic chiasm that leads to visual disturbances

Pathophysiologies of macroadenomas (hyperprolactinemia)

invasion of local structures and compression of hormone secreting cells that leads to hypopituitarism

CNS effects of hyperprolactinemia

headaches

Clinical manifestations of hyperprolactinemia

inhibits pulsatile secretion of GnRH, alters release of LH and FSH, hypogonadism

Hyperprolactinemia treatment

alter medications, use dopaminergic agonists, surgery, radiation

Kallmann syndrome

defective migration of GnRH cells and formation of olfactory bulb, leads to reduced GnRH, anosmia

Clinical manifestations of Kallmann syndrome

deafness, cerebellar dysfunction, cleft lip, or high arched palate

What causes Kallmann syndrome

hyposecretion of prolactin

What hormones does the posterior pituitary release

ADH and oxytocin (made in hypothalamus)

Normal function of ADH/vasopressin

conserve body water and prevent changes in plasma osmolality

What increases ADH

intravascular volume loss, stress, trauma, pain, exercise, nause, nicotine, heat, morphine

What decreases ADH

decrease in plasma osmolality, increase in intravascular volume, hypertension, increase in estrogen, progesterone, angiotensin, ingestion of alcohol

Increased ADH

syndrome of inappropriate antidiuretic hormone

SIADH

increased reabsorption of water in collecting ducts of kidneys

What causes SIADH

small cell lung cancer, medications, CNS and lung infections

Clinical manifestations of SIADH

hypervolemia/weight gain, polydipsia, GI symptoms, muscle twitch/seizures

SIADH treatment

fluid restriction, monitoring of Na levels and neurologic symptoms, use of vasopressin receptor antagonisits

Insufficiency of ADH

diabetes insipidus

Causes of diabetes insipidus

inadequate response of renal tubules to ADH, polydipsia, gestational, amphotericin B, demeclocycline

Diabetes insipidus pathophysiology

inability to concentrate urine, increased plasma osmolality, dehydration, hypernatremia

Clinical manifestations of diabetes insipidus

polyuria, polydipsia, nocturia, hydronephrosis

Treatment of diabetes insipidus

fluid replacement, treatment of underlying disorders, correct electrolytes, medications

Oxytocin function

mediates uterine contraction and sucking reflex

When is plasma oxytocin increased during parturition

when the fetus enters the birth canals

What does increased oxytocin secretion mean

does not initiate rhythmic uterine contractions

What does oxytocin do immediately after birth

causes uterine contraction to limit blood flow/loss