#2- Pituitary Flashcards
This one of the earliest signs of pituitary tumor or abnormal growth
Bitemporal hemianopia
Aka loss of aspects of vision
Compression of optic chiasm—> peripheral vision loss
The hypothalamus regulates:
Appetite, sleep, activity of the ANS, and pituitary hormone secretions
Posterior pituitary hormones
ADH (vasopressin) and Oxytocin
Anterior pituitary hormones
TSH, ACTH, LH, FSH, prolactin, GH
TRH axis
TRH in hypothalamus–> TSH via thyrotroph cells of ant. Pit—> thyroid gland to release T3 and T4 for metabolism regulation & calcitonin from parathyroid glands for minor role in blood calcium levels
GHRH axis
GHRH via hypothalamus—> GH/somatotropins via somatotroph cells—> insulin like growth factors (IGFs) from liver for cell growth and cessation of apoptosis
Most frequent pediatric intracranial neoplasm
Craniopharyngioma
- arises from squamos cell nests in primitive Rathke pouch
Why is the pituitary gland known as the “master gland”
It influences the hormonal secretions of other endocrine glands via releasing trophic hormones
CRH axis
CRH via hypothalamus—> ACTH via corticotroph cells of the anterior pit—> glucorticoids (CHO metabolism and stress response) and mineralcorticoids (weakly: aldosterone to regulate BP and water reabsorption) via adrenal glands
GTRH axis
GTRH via hypothalamus—> FSH and LH via gonadotroph cells of ant. Pit—> ovaries and testes which function in growth of ovaries and testes, output of sex hormones, regulating menstrual cycle in women, and male androgen release
- LH: testosterone and progesterone
- FH: estradiol and inhibin
Role of somatostatin:
Inhibitory hormone via hypothalamus which inhibits TSH and GH/somatotropins via somatotroph cells in the ant. Pit
Role of dopamine:
Inhibitory hormone via hypothalamus which inhibits prolactin stimulation by TRH via lactotroph cells in the anterior pituitary
Vasopressin Role
Posterior pituitary hormone
Stimulates kidneys to reabsorb water; regulates BP
Oxytocin role
Posterior pituitary hormone
Stimulates breasts and uterus for contraction of uterus and prostaglandin release
Prolactin inhibition and fx:
- dopamine
- drugs mimicking dopamine
Fx: stimulates milk production in breast tissue
Prolactin stimulation:
- TRH
- estrogen
- nipple sucking
Role of somatostatin released by the hypothalamus:
- inhibits TSH
- inhibits GH
Two inhibitory enzymes released by the hypothalamus:
Somatostatin
Dopamine
Tumor effects depend on
1- Hormones: amount and type
2- Tumor: size and location
3- Patient: age
Functioning tumors release which 2 hormones:
GH or prolactin
MC adenoma
Microadenoma
- benign but may be functional
Microadenoma size and hormone release
<1 cm/10 mm and prolactin
Macroadenoma size and hormone release
> 10 mm and GH
Benign adenoma more common in adults
Meningioma
- always non-functional
Prolactinoma s/s in women
MC microadenomas
- menstrual irregularities; menopause; pain w/ sex; vaginal dryness; and osteoporosis
- 30-80% w/ galactorrhea: may be B/L or unilateral
S/s Prolactinoma in men:
Decreased libido, erectile dysfunction and infertility (gynecomastia is rare)
These symptoms arise as adenomas increase in size
Compression s/s aka visual field deficits
Hyperprolactinemia differential dx:
1- pregnancy (MC and #1 to think of) 2- drugs that inhibit dopamine 3- ESRD/cirrhosis 4- endocrine disorders: (aka too much TRH being release) hypothyroidism or adrenal insufficiency 5- hypothalamic or pituitary pathology
W/u for prolactinoma:
Check TSH and prolactin levels (pregnancy test if female)
1st: MRI w/ thin cuts/contrast
2nd: CT w/ contrast if sella abnormal
Treatment for prolactinoma:
1- most microprolactinomas do not progress—> so mild s/s? Then yearly MRI and w&w
2- Meds: Bromocriptine—> dopamine agonist and tumor shrinks
3- Surgery: Transphenoidal pituitary adenectomy
Excessive GH in adults leads to
Acromegaly
excessive GH in children leads to
Gigantism
MC cause of excessive GH
Functional pituitary adenoma
- 70% of acromegalics have a macroadenoma; 1/3 of functional adenomas secrete GH
Anterior lobe of hypothalamus secretes hormones via
Pituitary Portal circulation
Posterior lobe of hypothalamus secretes hormones via
Directly by a neural network in the pituitary stalk to the posterior lobe
