Endocrine Overview & Hypopituitary Pathology Flashcards
What gland is the master regulatory gland?
Pituitary
What hormones are released from the posterior pituitary?
ADH (Vasopression) and oxytocin
What hormones are made in the posterior pituitary?
None
What hormones are made and released from the anterior pituitary?
ACTH, GH, PRL, LH, FSH, TSH
What hormone released by the pituitary involves a positive feedback loop?
Oxytocin
What hormone released by the pituitary is always inhibited in a normal system?
Prolactin
What is the anterior pituitary also called?
Adenohypophysis
What is the posterior pituitary also called?
Neurohypophysis
What is the primary function of prolactin?
Milk production in women
What is the primary function of oxytocin?
Uterine contractions and milk let-down
What hormone functions in milk let-down?
Oxytocin
What is the primary function of FSH in women?
Maturation of the ovary
What is the primary function of FSH in men?
Maturation of spermatozoa by acting on Sertoli cells
What is the function of LH in women?
Estrogen production and stimulation of ovulation
What is the function of LH in men?
Testosterone production
What hormone stimulates ovulation?
Luteinizing hormone (LH)
What hormone functions in milk production and lactation?
Prolactin
What hormones are released by the hypothalamus to stimulate the anterior pituitary?
- Thyrotropin releasing hormone (TRH)
- Gonadotropin releasing hormone (GnRH)
- Growth hormone releasing hormone (GHRH)
- Corticotropin releasing hormone (CRH)
What does the deiodinase enzyme require to convert T4——>T3?
Iodine and bile
What is the active form of thyroid hormone?
T3 (Triiodothyronine)
What hormone inhibits TRH release from the hypothalamus?
T3 (Triiodothyronine)
What hormone inhibits TSH release from the anterior pituitary?
T4
When the hypothalamus releases TRH what does it target and what does that target organ/gland release?
Targets the adenohypophysis and the adenohypophysis releases thyroid stimulating hormone (TSH)
When the hypothalamus releases GnRH what does it target and what does that target organ/gland release?
Targets the adenohypophysis and the adenohypophysis releases follicle stimulating hormone and luteinizing hormone
When the hypothalamus releases GHRH what does it target and what does that target organ/gland release?
Targets the adenohypophysis and the adenohypophysis releases growth hormone
When the hypothalamus releases CRH what does it target and what does that target organ/gland release?
Targets the adenohypophysis and the adenohypophysis releases adenocorticotropic hormone (ACTH)
Where does the conversion of T4—->T3 occur?
Liver
What is hypopituitarism?
Decreased secretion of pituitary hormones
When does hypofunction of the anterior pituitary occur?
When roughly 75% of the parenchyma is lost or absent
What are common etiologies of pituitary hypofunction?
Tumor or mass lesions, Pituitary surgery or radiation (iatrogenic), Pituitary apoplexy or ischemia (Sheehan’s)
What is Sheehan’s syndrome?
Rare complication occurring during pregnancy when a woman is having early labor contractions and does not breathe causing rupture of capillaries in the pituitary resulting in pituitary ischemia
A Valsalva maneuver in weight lifting may be associated with what syndrome of hypopituitarism?
Sheehan’s syndrome
What is the main etiology of panhypopituitarism?
Pituitary apoplexy/ischemia (see “common etiologies of pituitary hypofunction”)
What is panhypopituitarism?
Global decrease in all (anterior) pituitary hormones
What is the cause of pituitary dwarfism?
Hyposecretion of growth hormone during childhood
Pituitary dwarfism will result in ____ small stature
Proportionately
What causes hypogonadism?
Decreased blood gonadotropins including FSH and LH
What is a sign of hypogonadism?
Testicular or breast atrophy
To measure gonadotropin levels in males, you would measure blood ____ levels
testosterone
What are examples of congenital syndromes causing hypogonadism?
Kallman syndrome and Prader-Willi syndrome
What are examples of acquired causes of hypogonadism?
Pituitary tumor, steroid abuse, and TRT
What is the mechanism for how testosterone replacement therapy inhibits testosterone production in males?
- TRT will ^blood testosterone far above normal levels for pt’s age
- ^testosterone inhibits hypothalamus from producing GnRH, therefore reducing FSH & LH secretion from ant. pituitary resulting in low sperm count
What hormone inhibits GnRH secretion from the hypothalamus in males?
Testosterone
What hormone inhibits GnRH secretion from the hypothalamus in females?
Estrogen
Kallmann Syndrome and Prader-Willi Syndrome are congenital forms of hypogonadism due to issues with what structure?
Hypothalamus
What is Kallmann Syndrome?
Genetic condition resulting in the failure to trigger puberty in males and females due to a failure of hypothalamus to produce GnRH (Hypogonadotrophic hypogonadism)
What are signs and symptoms of Kallmann Syndrome?
Infertility, anosmia, cleft lip and palate
(associated with midline defects)
18 year old male patient presents to your office complaining of a lack of smell. Upon inspection you notice that he has a cleft palate. A blood panel shows low levels of FSH and LH in the blood and the patient also reports difficulty maintaining an erection in the morning. What is the likely diagnosis?
Kallmann Syndrome
What is Prader-Willi Syndrome?
genetic condition of hypogonadism and possible GH deficit
What are signs and symptoms of Prader-Willi Syndrome?
- Low muscle tone
- short stature
- incomplete sexual development
- Low IQ/poorly behaved
- chronic hunger –> excessive eating –> morbid obesity
13 year old male patient presents to your office with his mother. The mother reports that she cannot turn away for a minute or else her son has her hand in the cookie jar to eat cookies throughout the day. The boy is morbidly obese, short, and has very little muscle tone. His mother reports holding him back two years in the 9th grade for failing basic science courses. The boy reports that he just can’t help himself and is always feeling hungry. What is the likely diagnosis?
Prader-Willi syndrome
What is Turner’s syndrome?
XO trait in females resulting in male characteristics, amenorrhea, a short stature, and webbed neck
(Kallman & Prader-Willi syndromes can be confused with this)
What is empty sella syndrome?
Radiologic term for an enlarged sella containing a thin, fattened pituitary at the base
What causes empty sella syndrome?
Congenitally defective or absent diaphragma sella which permits transmission of CSF pressure into the sella
20 year old female patient presents with general endocrine disturbances including hypersecretion of breast milk despite not being pregnant. She also reports fewer menstrual cycles and recently has gained a considerable amount of weight and stretch marks on her stomach. Radiograph of the skull reveals a broad, flat sella turcica. What is the likely diagnosis?
Empty Sella syndrome
What are examples of endocrine disturbances caused by empty sella syndrome?
- hyperprolactinemia
- oligomenorrhea/amenorrhea
- frank hypopituitarism
- acromegaly
- diabetes insipidus
- cushing syndrome
