MNSR 41 - Endocrinology ; Hormones of the Adenohypophysis.. Flashcards
what part of the anterior pituitary gland are responsible for chief source of trophic hormones
pars distalis
trophic hormones function
regulate hormone secretion from another endocrine gland
name six different cell types associated with anterior pituitary gland
Corticotrophic – ACTH Thyrotrophic – TSH Gonadotrophic – FSH & LH Somatotrophic – GH Lactotrophic – Prolactin Chromophobic – unknown
Thyroid Stimulating Hormone name:
i) Structure
ii) Plasma half life
iii) Target Organ
iv) Control centre
i)Glycoprotein alpha chain (92 aa) beta chain (110 aa) ii)35-55mins iii)thyroid follicular cells iv)Thyrotrophin Releasing Hormone
Adrenocorticotrophic Hormone name;
i) Structure
ii) Plasma half life
iii) Target Organ
iv) Control centre
i)Peptide 39 amino acids ii) 5 - 10 mins iii)adrenal cortex iv)Corticotrophin Releasing Hormone
Follicle Stimulating hormone name; i)Structure ii)Plasma half life iii)Target Organ iv)Control centre
i)Glycoprotein alpha chain (92 aa) beta chain (115 aa) ii)60 mins iii)ovary - follicles testis - germinal epithelium iv)Gonadotrophin Releasing Hormone
Luteinizing Hormone name;
i) Structure
ii) Plasma half life
iii) Target Organ
iv) Control centre
i)Glycoprotein alpha chain (92 aa) beta chain (115 aa) ii)60 mins iii)ovary- ovulation corpus luteum testis- Leydig cells iv)Gonadotrophin Releasing Hormone
Prolactin name;
i) Structure
ii) Plasma half life
iii) Target Organ
iv) Control centre
i)Polypeptide 199 amino acids ii)30 mins iii)mammary gland ? male prostate iv)PRIH = dopamine
Growth hormone (Somatotrophic hormone) name;
i) Structure
ii) Plasma half life
iii) Target Organ
iv) Control centre
i)Polypeptide 191 amino acids ii)30 mins iii)liver - somatomedin iv)Growth hormone releasing hormone
What does thyroid stimulating hormone stimulate?
Stimulates thyroid to release two hormones;
T4 – Thyroxine
T3 - Triiodothyronine
what organs and parts of the pituitary gland help control negative feedback of Thyroid Stimulating Hormone (TSH) to operate?
through the hypothalamus
Directly on the pars distalis
how is TSH secreted and what time of the day does its activity peak?
in a pulsatile/pulsating manner with peak activity at night
describe morphological action of TSH?
Stimulates growth in the size and number of the thyroid follicular cells
What is the overall impact of the TSH in the body?
May enhance the uptake of thyroid hormone by muscle cells
ACTH
Adrenocorticotrophic Hormone
Also called corticotrophin
where is ACTH released and what hormones stimulate the release of this hormone ACTH?
Released from pituitary in response to corticotropin-releasing hormone (CRH) from hypothalamus
What organ does Adrenocorticotrophic Hormone/ACTH target?
targeting the adrenal gland specifically the adrenal cortex
Adrenocorticotrophic Hormone/ACTH stimulates the synthesis and release of…
Glucocorticoids (e.g. cortisol)
Mineralocorticoids
Androgens (e.g. testosterone precursor)
How is ACTH secreted throughout and what time of the day is its peak?
Secreted in a pulsatile/pulsating manner during the day peaking in early morning and low in late evening
Long term effects of Adrenocorticotrophic Hormone/ACTH?
Initiating and maintaining the full development of the adrenal gland
What are the short term effects of Adrenocorticotrophic Hormone/ACTH?
Responds to “stress reaction” where any stress to the body will cause release of ACTH within seconds
How does negative feedback of Adrenocorticotrophic Hormone/ACTH operate?
- rise in cortical adrenal hormones leads to decreased ACTH and CRH
Other name of cortisol hormone?
stress hormone
where is cortisol hormone released?
Adrenal cortex
effects of cortisol hormone?
suppress immune system decrease serotonin decrease sensitivity of pain increase blood pressure increase blood sugar heightened memory and attention
What is the GRH and its function?
Gonadotrophin Releasing Hormone
Stimulates release of both Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH)
Why is Follicle Stimulating Hormone (FSH) sometimes called the gonadotrophins?
stimulate the gonads and are sometimes called gonadotrophins
How does Follicle Stimulating Hormone (FSH) affect females?
Stimulates growth of the follicles and stimulates oestrogen secretion by follicular cells
How does Follicle Stimulating Hormone (FSH) affect males?
Stimulates growth of the germinal epithelium in the seminiferous tubules of the testis
Function of Luteinizing Hormone/LH?
maintains the interstitial tissue of the testes and ovaries even when the gametogenic tissue is inactive
Other name of Luteinizing Hormone/LH in males
interstitial cell stimulating hormone (ICSH)
How does Luteinizing Hormone/LH affect males?
Stimulates the growth of the Leydig cells and the secretion of testosterone
How does Luteinizing Hormone/LH affect females?
causes luteinization of ovarian follicle after ovulation
forms corpus luteum, which produces progesterone
Controls the final step in ovulation where its release is stimulated by oestrogen levels
main function of prolactin
to cause development and production of milk in the breast or mammary gland which has already been stimulated by the gonadotrophins and sex hormones of pregnancy
what is a major stimulus for prolactin
tactile stimulation of the nipple by the suckling infant in postpartum lactating women
what mediates prolactin and what is required to activate them?
two linked receptors which require two prolactin molecules to activate
what effect does prolactin have on males?
In males it increases the LH receptors in the Leydig cells
what controls/inhibitory to prolactin?
being mainly inhibitory (dopamine) but TRH may stimulate secretion
what stimulates secretion of Growth Hormone/GH?
Growth Hormone Releasing Factor (GHRH)
Releases GH release from pituitary
what inhibits releases of Growth Hormone/GH?
Somatostatin
How does insulin Growth Factor-1 affect release of Growth Hormone/GH?
Stimulates somatostatin to inhibit GH release
Prevents GH release from the pituitary
Increases growth of peripheral tissues
physiological effect of Growth Hormone?
stimulation of amino acid transport and protein synthesis
what is the overall effect of the Growth Hormone on the appearance of the body?
growth of the individual though it also has metabolic effects
name of condition with absence of GH and excessive GH
The absence of GH in children leads to dwarfism
Excessive GH
Children: giantism (gigantism)
Adults: acromegaly
Pars Intermedia:
Boundary between the anterior and posterior lobes of the pituitary
Derived from similar tissue as the pars distalis and produces one single hormone:
Hormone released from Pars intermedia
Melanocyte Stimulating Hormone/ MSH
3 forms of MSH
alpha-MSH (13 amino acids similar to part of the ACTH molecule)
beta-MSH (18 amino acids)
gamma-MSH (12 amino acids)
effects of MSH/Melanocyte stimulating hormone
Affects the production and dispersion of melanin granules in the melanocytes
Skin & hair coloration in mammals
Tanning ability post UV exposure
name 2 hormones produced in hypothalamus and released in posterior pituitary gland
Anti-Diuretic Hormone
Oxytocin
what is the only structural difference in ADH and oxytocin
Differ in only two amino acid residues
oxytocin - 3rd amino acid Isoleucine 8th amino acid - Leucine
ADH - 3rd aa - phenylalanine 8th aa - arginine
half life of oxytocin and ADH
Oxytocin - 2-4 mins
ADH - 15-30mins
where specifically are oxytocin and ADH produced in the hypothalamus
the supraoptic and paraventricular nuclei
where are oxytocin and ADH transported and stored
Transported along the axons to the pars nervosa where they are stored until required
what receptor stimulates release ADH
Osmoreceptor cells detect changes in blood Na+ ion levels
A nerve impulse (afferent) travels to the pars nervosa and ADH is released
what effect does alcohol have on ADH?
Alcohol has an inhibitory effect on ADH release causing diuresis
name disorder of pars nervosa
Diabetes Insipidus
Diabetes Insipidus and its causes
A deficiency of ADH causes the disease diabetes insipidus (not related to diabetes mellitus)
failure of the collecting ducts to reabsorb water
consequences of diabetes Insipidus
excretion of very high volumes of pale (dilute) urine
most common causes of Diabetes Insipidus
is damage to the pituitary or hypothalamus due to head injury, infection, surgery, autoimmune reaction or any other source of harm to the region
Treatment of Diabetes Insipidus
lypressin or desmopressin, administered by nasal spray or injection
where is oxytocin expressed in the body?
Oxytocin receptors are expressed by the myoepithelial cells of the mammary gland, and in both the myometrium and endometrium of the uterus at the end of pregnancy.
2 process which involve oxytocin
Letdown reflex – release of milk during breast feeding (myoepithelial cell contraction)
Uterine contraction
Let-down Reflex
stimulation - infant suckling on nipple
Afferent sensory impulse reaches hypothalamus thru spinal cord
Activates oxytocin neurons in supraoptic and paraventricular nuclei
causes release of oxytocin from pars nervosa
oxytocin carried through blood vessels to mammary gland
causes myoepithelial cells of milk ducts to contract - release milk
target organ of let-down reflex
mammary gland to stimulate release of milk
why is oxytocin released in the uterus?
needed for;
cervial dilation
initiation of contractions during second and third stages of labour
to assist uterus in clotting the placental attachment point postpartum
how is synthetic oxytocin used
Slow IV infusion
Amplitude and frequency of contractions related to dose given
