Week 2 - Ant. Pituitary Flashcards
The pituitary gland lies in the _____ ______ just below the hypothalamus.
Sella turcica (“bony saddle”)
Pituitary is connected to the hypothalamus
by a little stalk called the _________,
which contains nerve fibers and small blood
vessels
infundibulum
The pituitary gland is composed of what 3 major parts?
Anterior
Posterior
Intermediate
What does the intermediate lobe of the pituitary gland secrete?
melanocyte stimulating hormone (MSH)
T/F: Most hypothalamic & pituitary hormones
are released in a pulsatile or burst-like
manner
True
What are the 5 hormones secreted by the Anterior Pituitary?
- Growth hormone (GH)
- Thyroid-stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- Gonadotropic hormones (FSH, LH)
- Prolactin (PRL)
T/F: The posterior pituitary is really a neural
extension of the hypothalamus
True
What are the 2 hormones secreted by the Posterior Pituitary?
- Antidiuretic hormone (ADH)
2. Oxytocin
What is the other name for the anterior pituitary?
Adenohypophysis
What is the other name for the posterior pituitary?
Neurohypophysis
What is the other name for growth hormone secreted by the anterior pituitary? Which cells secrete them?
Somatropin; secreted by somatotrophs
What is the hypophysiotropic hormone related to growth hormone?
Growth hormone releasing hormone (GHRH)
What are 9 stimulators of growth hormone release?
- Hypoglycemia/fasting
- Glucagon
- Ghrelin
- Estrogen
- Androgens (during puberty)
- Strenuous exercise
- Nicotine
- Vit B3
- Deep Sleep
What is the secretion amount of growth hormone in young adolescents and healthy adults?
Young adolescents: 700mcg/day
Healthy adults: 400mcg/day
Secretion is greatest about ____ hour/s after sleep onset.
1 hour
T/F: Nearly 50% of total GH secretion occurs during slow-wave sleep. What stage of sleep is this?
True; Stage 3 and 4 of NREM sleep
T/F: Sleep deprivation increases growth hormone release.
FALSE! It suppresses growth hormone release
What are 4 inhibitors of growth hormone?
- Somatostatin (Growth-hormone inhibiting factor)
- Hyperglycemia, increased free fatty acids
- Glucocorticoids (cortisol)
- Increased Dihydrotestosterone
Growth hormone is primarily a/an _________ hormone
anabolic
Growth hormone increase height in childhood by stimulating multiplication of which cells?
Chondrocytes
Excess growth hormone secretion in childhood is which disorder?
Pituitary gigantism
Prolonged growth hormone excess after closing of epiphyseal plates, causing thick bones in jaw, fingers, and toes is which disorder?
Acromegaly
Growth hormone stimulates production of insulin-like growth factor (IGF-1,2) from the liver. What are 6 effects of this on peripheral tissue?
- ↑ muscle mass
- Promotes lipolysis
- ↑ protein synthesis
- ↓ liver uptake of glucose
- Stimulates immune system
- Improve calcium retention
Adreno-corticotropic hormone (ACTH) is also known as ________ and is secreted by which cells in the anterior pituitary?
Corticotropin; corticotrophs
What is a hypophysiotropic hormone related to ACTH? What does it do?
Corticotropin-releasing hormone (CRH); stimulates ACTH in a pulsatile manner
What is the function of ACTH?
Stimulates adrenal cortex to release corticosteroids (specifically from the zona fasciculate & zona reticularis)
Which cells secrete thyroid-stimulating hormone (TSH)?
Thyrotrophs
Which sex hormone will increase sensitivity of thyrotrophs to TRH?
Estrogens
What is the hypophysiotropic hormone for TSH?
Thyrotrophin-releasing hormone (TRH)
What are 3 inhibitors of TSH?
- Somatostatin
- Dopamine
- Cortisol
How does cortisol inhibit TSH?
It impairs sensitivity of the pituitary to TRH; may lower serum to undetectable levels
What are 3 functions of TSH?
- Thyroid hormone secretion (T4 and T3)
- Hyperplasia/hypertrophy of thyroid gland
- Vascularization of thyroid gland
_____ is the primary marker used to assess thyroid function.
TSH
T/F: Levels of TSH are proportional to the concentration of
thyroid hormone in the plasma
FALSE! Levels are inversely proportional
Which 2 hormones are secreted by cells called gonadotrophs?
FSH and LH
What is the hypophysiotropic hormone related to FSH and LH?
Gonadotropin-releasing hormone (GnRH)
What is the overall function of FSH?
Stimulates growth of germ cells
What is the function of FSH in women? Which form of estrogen levels rise?
Ovary: stimulates growth of Graafian follicles to maturation; estradiol levels rise
What is the function of FSH in men?
Testes: stimulates spermatogenesis
What role does cortisol play in relation to LH?
Inhibits gonadotroph response to GnRH
Low frequency pulses of GnRH will produce secretion of which hormone? High frequency?
Low: FSH
High: LH
What is the overall function of LH?
Stimulates sex-hormone secretion
What is the function of LH in females?
Ovary: acute rise in LH (LH surge) triggers ovulation; stimulates corpus luteum development and secretion of progesterone
What is the function of LH in males?
Testes: Stimulates Leydig cells to produce testosterone
Prolactin is secreted by which anterior pituitary cells?
Lactotrophs
Which substances or physical stimulus increases prolactin secretion?
- Serotonin
- Stressors (surgery, exercise, hypoglycemia, acute MI)
- Nipple stimulation (in non-PG women)
What substance binds to lactotrophs and inhibits prolactin secretion?
Dopamine
What does Bromocriptine do to prolactin secretion?
Decreases it
What does dopamine agonists do to prolactin secretion?
Increases it
Extrapituitary secretion of prolactin occurs in T-cells, where are receptors found?
Prolactin receptors found in T & B-cells, macrophages
What are the 3 functions of prolactin related to breasts?
- Promotes lactation
- Increases breast size
- Sodium retention
What are the 3 functions of prolactin related to sexual gratification?
- Suppresses ovulation, fertility
- Suppresses sexual arousal (opposes dopamine)
- Accounts for male “refractory” period after sex
Elevated prolactin leads to _____________ which interferes with pulsatile secretion of LH & FSH.
Hypogonadism
Elevated prolactin in women can lead to shortening of which phase? What is the result?
Shortens luteal phase; results in annovulation, oligomenorrhea/amenorrhea, and infertility
Elevated prolactin in men can lead to decreased synthesis of which hormone? What is the result?
Decreased testosterone synthesis; results in decreased spermatogenesis, low libido, impotence, and infertility
What is the preferred method for visualizing the hypothalamus-pituitary?
MRI (with or without contrast)
What is the most common type of hypothalamic-pituitary abnormality?
Pituitary adenoma (10-25% of all intracranial neoplasms)
What are 3 types of pituitary adenomas?
- Benign adenoma
- Invasive adenoma
- Carcinoma
Are the majority of adenomas: micro-adenomas or macro-adenomas?
Microadenoma
What is the disease associated with hyper secretion of ACTH?
Cushing’s Disease
What is the most common s/sx of prolactinoma?
Galactorrhea
What is the most frequent manifestation of functional adenomas? What is this due to?
Hypogonadism; suppression of GnRH function from elevated prolactin, ACTH, and GH
T/F: Panhypopituitarianism is a very common condition associated with functional adenomas.
FALSE! They are less common (<20%)
Invasive adenomas: sellar enlargement causes which 2 things?
- Headaches
2. Visual loss/changes
T/F: Patients presenting with bitemportal hemiaopsia or unexplained visual field defects or visual loss should be considered to have a pituitary or hypothalamic disorder until proven otherwise.
True
T/F: Pituitary adenomas in children are common
FALSE! They are rare. Most common are craniopharyngiomas and other hypothalamic tumors.
Enlargement of a pituitary mass may cause which 2 things?
- Mass effect
2. Stalk effect
Mass effect of the pituitary causes which 2 problems?
- Exert pressure on nearby tissues
2. Intracranial pressure
The stalk effect causes what problem?
Secretion of large amounts of prolactin
How is primary hypopituitarism caused?
Destruction of the pituitary
How is secondary hypopituitarism caused?
Deficiency of hypothalamic stimulatory factors
What percent of the anterior pituitary must be destroyed for symptoms to manifest from hormonal deficit?
75%
What are 6 causes of hypopituitarism?
- Pituitary adenoma
- Pituitary apoplexy
- Sheehan syndrome
- Empty sella syndrome
- Trauma
- Infiltrative conditions
Which hypopituitarism condition has spontaneous hemorrhage of the pituitary, usually into a pre-existing adenoma? Symptoms include sudden onset HA and diplopia.
Pituitary apoplexy
What is the most common cause of ischemic necrosis of the pituitary?
During pregnancy anterior pituitary enlarges, but the blood supply does not increase: pituitary prone to ischemia
During delivery, hemorrhage & shock may occur, resulting in further underperfusion of the anterior pituitary
May cause pituitary collapse,
failure to lactate, amenorrhea following pregnancy & hypothyroidism are often the first symptoms
Sheehan syndrome (“Post-partum necrosis of the pituitary”)
Which condition occurs when the subarachnoid space extends into the sella turcica, partially filling it with cerebral spinal fluid and causes enlargement of the sella, flattening the pituitary gland?
Empty Sella Syndrome
Which type of sella syndrome results from congenital incompetence of the diaphragm sellae? It is the most frequent cause of enlarged sella turcica, is associated with obesity & hypertension in women, and can be a sign of idiopathic intracranial hypertension.
Primary
Which type of sella syndrome causes: pituitary gland regression after an injury, surgery, or radiation therapy, postpartum pituitary infarction (Sheehan syndrome), PRL or GH-secreting pituitary adenomas. May undergo
hemorrhage with infarction & cause contraction of the
overlying suprasellar cistern downward into the sella.
Secondary
What is the most common clinical feature of empty sella syndrome?
Headache (approx 48%)
T/F: Empty sell syndrome usually doesn’t need treatment, but should be differentiated from pituitary adenomas
True
Which condition has a short stature resulting from a medical condition caused by abnormal/slow growth?
Dwarfism
Between achondroplasia and pituitary dwarfism, which is more commonly the cause of dwarfism?
Achondroplasia (approx 70% of cases)
Which form of dwarfism is generalized slow growth where patients do not go through puberty?
Treatments for this condition include replacement of relevant hormones.
Panhypopituitarism (~2/3 of cases)
Which form of dwarfism do patients generally undergo normal sexual maturation and they are capable of having children?
Isolated growth hormone deficiency (~1/3 of cases)
Peak incidence of pituitary adenomas is between which ages?
30-60 y/o
T/F: Pituitary adenomas are mostly isolated, solitary lesions w/out associated neoplasms
True
Approx. 10% of pituitary adenomas are considered_______, being asymptomatic and non-functional
Incidentalomas
Approx ____% of pituitary adenomas are associated with multiple endocrine neoplasia (MEN) type 1
3
T/F: Pituitary adenomas are usually composed of multiple cell types that all secrete different hormones
FALSE! They are usually composed of a single cell type that secretes a single hormone (i.e. lactotrophs secreting prolactin)
Which pituitary adenoma is associated with elevated plasma prolactin, and interferes with HPG-axis?
Prolactinoma
What are 2 pharmaceutical treatment options for treating a prolactinoma?
Bromocriptine and Cabergoline
What are 3 ND treatments for a prolactinoma?
- Vitex agnus-castus
- Dopamine synthesis cofactors (B6, folate, tyrosine, Mg)
- GABA
What is the second most common functional adenoma of anterior pituitary, subtle changes in growth (e.g. shoe size) may be the first symptoms?
Growth hormone (somatotropin) adenoma
What is a general increase in body size from excessive growth hormone secretion that occurs before growth plates close at the ends of the long bones (in children, teens)?
Gigantism
Which condition has effects of excessive growth hormone that occurs after the growth plates have closed (late teens, adults). It has physical symptoms of growth of bones in hand, feet, face, skull, jaw (jaw protrusion w/ spreading of teeth, & growth of viscera, skin, soft tissue, prominent brows, gapped teeth, huge feet and hands; usually not excessively tall or large overall; coarsening of facial features
Can also see secondary diabetes (via insulin resistance), hypertension, muscle weakness, congestive heart failure (diastolic dysfunction), arthritis, obstructive sleep apnea, and osteoporosis
Acromegaly
What are 4 therapeutic interventions used for treating growth hormone adenomas?
- Transsphenoidal microsurgery
- Somatostatin analogues (ocreotide acetate or LAR)
- Dopamine agonists (Cabergoline)
- GH receptor antagonist (Pegvisomant)
Which condition has ACTH hypersecretion resulting in elevated cortisol levels? It results from microadenomas <10mm in diameter and causes bilaterial adrenal hyperplasia. Circadian rhythm of ACTH secretion is suppressed, there is abnormal negative feedback in the HPA-axis. Usual age of onset is 20-40 years
Cushing disease
Which condition has the following characteristics?
- Obesity (with central fat pattern), round (moon) face, hirsutism, easy bruising, poor wound healing, purple striae
- Presence of hypertension, diabetes,osteopenia/osteoporosis, superficial fungal infections, and menstrual/mental abnormalities
Cushing’s Syndrome
What are the 3 screening tests for diagnosing Cushings disease?
When diagnosing, pick 2 of the 3:
1. 24-hour free urine cortisol
2. Elevated midnight salivary cortisol on 2 separate nights
3. 1 mg dexamethasone suppression test (positive if AM cortisol is persistently
elevated in the morning after administration of dexamethasone)
What are the 4 medications used to treat Cushing’s syndrome?
No drug currently successfully suppresses ACTH secretion
- Ketoconazole: inhibits adrenal steroid synthesis
- Metyrapone: blocks cortisol synthesis
- Aminoglutethimide
- Mitotane: adrenolytic: causes adrenal atrophy
