Anterior Pituitary Flashcards
what 6 hormones are secreted by the anterior pituitary?
- prolactin (PRL): acts on mammary gland to promote milk production
- growth hormone (GH): everything (more later)
- thyroid stimulating hormone (TSH): tells thyroid glands to secrete T3 and T4
- adrenocorticotropic hormone (ACTH): tells the adrenal cortex to secrete cortisol and aldosterone
- follicle stimulating hormone (FSH): tells ovary to develop follicles and tells testes to produce sperm
- luteinizing hormone (LH): tells ovaries to ovulate follicles and tells testes to secrete testosterone
what cell types secrete which hormones in the anterior pituitary?
somatotrope cells make growth hormone
lactotropes produce prolactin
thyrotropes produce thyroid-stimulating hormone
corticotropes produce adrenocorticotropic hormone
gonadotropes produce FSH and LH
what controls synthesis and secretion of ALL anterior pituitary hormones?
the hypothalamus, which secretes regulatory/releasing factors
PRH: prolactin releasing
PIH: prolactin inhibiting (dopamine)
TRH: thyrotropin releasing
CRH: corticotropin releasing
GHRH: growth hormone releasing
GHIH: growth hormone inhibiting
GnRH: gonadotropin releasing
how are hypothalamic neurohormones carried directly to the anterior pituitary?
via the hypothalamic-pituitary portal system, which involves 2 capillary beds connected by portal vessels; allows for a rapid response with little dilution of hormones secreted from the hypothalamus as these factors (releasing and inhibitory hormones) do NOT enter the general circulation
what are the 3 families of anterior pituitary hormones?
- growth hormone and prolactin family
- pro-opiomelanocortin family (ACTH)
- glycoprotein family: TSH, LH, FSH
describe regulation of prolactin secretion
inhibition: dopamine released from neurons in the hypothalamus suppress prolactin synthesis and secretion from the anterior pituitary; suckling inhibits dopamine release
stimulation: PRH and TRH from the hypothalamus and estrogen from the ovary stimulate prolactin release from the anterior pituitary following the stimulus of suckling
what are the 2 functions of prolactin in the mammary gland?
- mammary gland development: increased alveolar number
- lactogenesis (milk production): stimulates transcription of genes that encode milk proteins
describe hypothalamic regulation of growth hormone secretion
- GHRH: releasing; produced and released in hypothalamus
- GHIH/somatostatin: inhibiting; widely distributed in CNS, GI tract, and pancreas
what are the 2 MAIN functions of growth hormone? also describe the long one
- acute metabolic effects
- long term body growth effects via stimulation of insulin-like growth factor 1 release from the liver
IGF-1 does (4)
1. promotes protein deposition
2. enhances fat utilization
3. decreases carbohydrate metabolism (antagonizes insulin action)
4. stimulates bone and cartilage growth
what can be caused by disruptions in growth hormone? (2 from increased GH, 1 from decreased GH)
increased GH:
1. gigantism: abnormal growth due to an excess of GH BEFORE bone growth plates have fused (proportionate growth)
2. acromegaly: abnormal growth due to an excess of GH AFTER bone growth plates have fused (disproportionate growth)
decreased GH:
1. dwarfism: deficiency of GH before the bone growth plates have fused; due to pituitary tumor
if cortisol levels are high, what do we expect ACTH levels to be and why? what does the opposite suggest?
when cortisol is high, would expect ACTH to be low, since cortisol negatively feeds back to decrease ACTH levels and vice versa
if cortisol is high and ACTH is also high, could indicate a pituitary tumor
describe the structure of TSH, FSH, and LH
all composed of two subunits
have a common alpha unit that is the same among all three, then a unique beta unit that confers specificity and is unique to each hormone
what can result from disruptions in TSH?
increased TSH: secondary hyperthyroidism characterized by rapid weight loss, increased appetite, increased drinking, increased urination, and hyperactivity and nervous behavior
decreased TSH: secondary hypothyroidism characterized by weight gain WITHOUT increased food intake, increased thirst and drinking, and lethargic behavior
give 5 endocrine based disorders caused by anterior pituitary gland dysfunction and give the hormones disrupted in each
- hyper and hypothyroidism: disruption of TSH and thyroid hormone
- cushing’s disease: increased ACTH and cortisol
- addison’s disease: decreased ACTH, cortisol, and aldosterone
- acromegaly and dwarfism: disruption of growth hormone
- infertility/delayed onset of puberty: disruption of gonadotropins and sex steroid hormones
what can anterior pituitary hormone deficiency result from? (2)
- isolated defect in the synthesis and secretion of a single hormone
- panhypopituitary: deficiencies in several hormones due to traumatic injury to pituitary, or a tumor that destroys pituitary cells or connection to hypothalamus and leads to multiple problems in sexual maturation, adrenal, and thyroid function
