Hypothalamic Pituitary Relationships Flashcards
The communications between the hypothalamus and ________ _____ are neural and hormonal
Anterior pituitary
Hormones of anterior pituitary
ACTH TSH FSH LH GH Prolactin
What is a hallmark symptom of pituitary tumors?
Vision changes d/t impingement of optic chiasm and optic n
What is the direct route of delivery of hormones from the hypothalamus to the anterior pituitary?
Hypothalamic hypophysial portal system
T/F: Hormones from the anterior pituitary appear in high concentrations in systemic circulation
False; they have high concentration within the gland itself
The anterior pituitary has neural and hormonal signals with the hypothalamus. The posterior pituitary has ____ signals only
Neural
The anterior pituitary is a collection of endocrine cells; the posterior pituitary is a collection of ______ whose cell bodies are located in the hypothalamus
Axons
The cell bodies in the hypothalamus that communicate with the posterior pituitary are associated with what 2 nuclei? What neuropeptides do they secrete?
Supraoptic nucleus (SON) = secretes ADH
Paraventricular nucleus (PVN) = secretes oxytocin
Compare/contrast primary vs. secondary vs. tertiary endocrine disorders
Primary = at the level of peripheral gland
Secondary = problem with pituitary
Tertiary = problem with hypothalamus
Hormone families of the anterior pituitary are organized by structural and functional homology. What are the 3 families of the anterior pituitary?
ACTH family = corticotrophs; secrete ACTH
TSH, FSH, LH family = thyrotrophs (secrete TSH); gonadotrophs (secrete FSH and LH)
GH, Prolactin family = somatotrophs (secrete GH), lactotrophs (secrete prolactin)
Match the releasing hormone with its target in anterior pituitary and hormone secreted:
TRH
Thyrotrophs —> TSH
Match the releasing hormone with its target in anterior pituitary and hormone secreted:
CRF
Corticotrophs —> ACTH
Match the releasing hormone with its target in anterior pituitary and hormone secreted:
GnRH
Gonadotrophs —> LH, FSH
Match the releasing hormone with its target in anterior pituitary and hormone secreted:
GHRH vs. somatostatin
GHRH —> somatotrophs —> GH
Somatostatin inhibits somatotrophs secretion of GH
PIF (dopamine) from hypothalamus acts on ______ in anterior pituitary to inhibit secretion of _____
Lactotrophs; PRL
Activity of endocrine axes are maintained at a set point, often secreting hormones in pulsatile manner and entrained to circadian rhythms. What are the axes associated with the anterior pituitary gland?
Hypothalamic-Pituitary-Gonad (HPG)
Hypothalamic-Pituitary-Liver
Hypothalamic-Pituitary-Prolactin
Hypothalamic-Pituitary-testis/ovary
Hypothalamic-Pituitary-thyroid
Hypothalamic-Pituitary-Adrenal
Rare disease characterized by excessive growth of soft tissue, cartilage, and bone in the face, hands, and feet; caused by prolonged and excessive secretion of growth hormone in adult life
Acromegaly
Physical findings of acromegaly
Prominent supraorbital ridges Lower teeth separation Prominent lower jaw Cardiomegaly Organomegaly Hyperglycemia Enlarged head circumference Hypertension Large hands Accelerated osteoarthrosis Increased heel-pad thickness on x-ray Large feet
Growth hormone is produced by somatotropes
It targets _____ and ______ (organs)
The GH receptor is linked to _______ signaling
Liver; bone
Jak-stat
Growth hormone is inhibited by ____ and _____ as part of a negative feedback mechanism
Somatostatin (GHIH)
IGF-1
What are the 2 primary stimulators of GH secretion?
Fasting/hunger/starvation
Hypoglycemia
[also puberty hormones, exercise, sleep, and stress]
GH binds directly to target cells in ____ and ____
Bones; muscle
GH binds directly to bones and muscle. What effect does it have on growth?
Hypertrophy - increase in size/volume of cells (ex: increases bone thickness)
GH binds directly to bones and muscle. What effect does it have on cell reproduction?
Hyperplasia = increase number of cells or proliferation rate via mitosis (ex: increase bone length)
GH binds directly to bones and muscle. What effect does it have on metabolism?
Increase glycogen and fat breakdown for energy to increase protein synthesis
Another name for growth hormone
Somatotropin
Another name for insulin-like growth factor 1 (IGF-1)
Somatomedin C
In a normal hypothalamic-pituitary-growth hormone axis, the hypothalamus releases either ______ and ______, or ______, which act at the anterior pituitary which will either be stimulated or inhibited to release growth hormone.
Two of the above will stimulate the release of growth hormone, which proceeds to the ______ which releases _______
Ghrelin; GHRH; somatostatin
Liver; IGF-1
Describe a primary GH insensitivity in terms of the HPGh axis
The liver is insensitive to GH, so GH levels rise
Describe a secondary GH insensitivity in terms of the HPGh axis
Secondary = problem with pituitary
Ghrelin and GHRH or somatostatin are released from hypothalamus, but GH cannot be released from anterior pituitary. IGF-1 does not get stimulated at all. GH levels are LOW
Describe a tertiary GH insensitivity in terms of the HPGh axis
Tertiary = problem with hypothalamus
Ghrelin, GHRH, and somatostatin not getting secreted from hypothalamus, no GH being released from anterior pituitary, IGF-1 not stimulated at all. GH levels LOW
Excess growth hormone causes 2 different conditions depending on closure of bone epiphyses (growth plates); what are they?
Gigantism if GH excess occurs prior to growth plate closure — due to IGF-1 stimulated long bone growth
Acromegaly if GH excess occurs after growth plate closure due to promotion of growth of deep organs and cartilaginous tissues
Growth promoting factors in the fed state are increased carb intake (leading to increased blood sugar and adequate insulin availability) and increased protein intake (leading to adequate amino acid availability)
These two factors act on the liver to produce IGF-1
What are the 3 anabolic activites encouraged by IGF-1?
Mitogenesis
Lipolysis
Differentiation
[increased activity of IGF-1 —> increased osteoblasts, collagen, and bone matrix]
What happens to GH if you have adequate insulin availability but inadequate amino acid availability?
GH is inhibited; liver will not produce IGF-1
Net result is weight gain d/t lipogenesis and carb storage