372 Hypopituitarism Flashcards
Considered the master glans together with the hypothalamus
Anterior pituitary
6 hormones by the anterior pituitary
- Prolactin PRL
- Growth hormone GH
- Adrenocorticotropic hormone ACTH
- Luteinizing hormone LH
- Follicle stimulating hormone LH
- Thyroid stimulating hormone TSH
Weight of the pituitary gland
600 mg
Blood supply of thre pituitary gland
Superior and Inferior hypophyseal arteries
Major blood source of the anterior pituitary gland allowing reliable transmission of hypothalamic peptide pulses without significant systemic dilution
Hypothalamic portal plexus
Direct ennervation of the pituitary gland
Hypothalamic neurons
True or false. Neuronal damage to the hypothalamus or pituitary stalk can alter ADH and oxytocin production
True
Hormones PRL is weakly homologous to
GH
Human placental lactogen hPL
Normal levels of prolactin in males? In females?
PRL
Females: 10-25 ug/L
Males: 10-20 ug/L
When is the highest secretory peaks of PRL
During REM sleep
Half life of PRL
50 minutes
What time does PRL peak
4:00-6:00 AM
How is PRL unique for other hormones
Central control mechanism is inhibitory
Weakly suppresses PRL
Glucocorticoids
Thyroid hormones
Induces PRL release
Vasoactive intestinal peptide (VIP)
Can transiently raise PRL levels
Exercise Meals Sexual intercourse Minor surgical procedures General Anesthesia Chest wall injury Acute myocardial infarction Acute stress
Can sucking induce PRL release? For how long
Yes. Sucking activates neural afferent pathways in the hypothalamus and increases PRL levels that lasts for 30-45 minutes
What is the effect of pregnancy on PRL levels
PRL levels increase 10x during pregnancy and deube within 2 weeks of parturition
Most abundant anterior pituitary hormone and constitute 50 of anterior pituitary cell population
Growth hormone GH
Hormone that is secreted in spikes to elicit GH pulses and the other hormone that sets the basal GH secretory tone
GHRH: elicits GH spikes
SRIH: sets BASAL GH tone
What induces GH and what suppresses GH
Estrogen: induces GH
Chronic glucocorticoids: suppresses GH
When is the highest peak of GH
Night
Leads to transient increase in GH
An hour of sleep Exercise Physical stress Trauma Sepsis
Contain the largest number of GH receptors
Liver and cartilage
Major source of circulating Insulin Growth like factor (IGF-1)
Liver
Conditions where IGF-1 is low
Cachexia
Malnutrition
Sepsis
Stimulator of ACTH synthesis and release
CRH
When does ACTH peak and when does it go nadir?
Peaks: 6 AM
Nadir: midnight
Regulates synthesis and release of LH and FSH
Hypothalamic GnRH
True or false. Main function of the HPA axis is to maintain metabolic hemostasis and mediate neuroendocrine stress response
True
What is the character of the GnRH secretion
Pulsatile every 60-120 minutes
Slows GnRH pulse frequency but enhances gonadotropin response to GnRH
Progesterone
Other hormone of the TGF beta faimy that suppresses FSH? Stimulates FSH?
Suppress FSH: inhibin
Stimulates FSH: activin
Gene responsible for hypothalamic dysfunction and hypopituitarism
HESX1 gene
Resulta from defective hypothalamic GnRH associated wiht olfactory bulb a genesis or anosmia
Kallmann syndrome
Mutation seen in Kallmann syndrome
X-linked KAL gene mutation which impair embryonic migration of GnRH neurons hypothalamic olfactory placode to the hypothalamus
GNRH deficiency. Genetically heterogenous disorder charcaterised by mental retardation, renal abnormalities, obesity, hexadactyly
Bardet-Biedl Syndrome
Prader willis syndrome is a contiguous gene syndrome results from deletion of what gene?
Deletion of the paternal copies of the SNRPN gene on chromosome 15q
In cranial irradiation leading to hypothalamic damage, what is the most common deficiency? 2nd most common?
Most common: GH deficiency
2nd: ACTH deficiency
Acute intra pituitary hemorrhage in postpartum
Sheehan syndrome
Endocrine emergency that results in severe hypoglycemia, hypotension and shock, CNS hemorrhage and death; results from acute intra pituitary hemorrhage
Apoplexy
Mean growth velocity. Peak growth rates in girls and boys?
Mean growth velocity: 6 cm per year
Peak growth girls: 12
Peak growth boys: 13
In insulin tolerance test for GH, what is the normal response
GH more than 3 ug/L
In TSH test for PRL, what is the normal response
PRL more than 2 ug/L and increase of more than 200% of baseline
In insulin tolerance test for ACTH, what is the normal response
Cortisol increase more than 7 ug/dl or more than 20 ug/dl
In CRH test for ACTH, what is the normal response
Basal ACTH increases to 2- to 4- fold and peaks at 20-100 pg/ml
In metyrapone tests for ACTH, what is the normal response
Plasma cortisol less than 4 g/dl
11 Deoxycortisol more than 7.5
ACTH more than 75 pg/ml
In standard ACTH stimulation with cosyntropin, what is the normal response
Cortisol more than 21 g/dl
In TRH test for TSH, what is the normal response
TSH should increase by more than 5 mU/L unless thyroid hormones are increased
When do you say a person is short stature
Height is more than 3 standard deviation below mean age
When is GH replacement contraindicated
Active neoplasm
Intracranial hypertension
Uncontrolled DM and retinopathy
Total daily dose of glucocorticoid replacement
Hydrocortisone: Not to exceed 25 mg/daily
Prednisone: 5 mg daily
Most common presenting feature of hypopituitarism
Hypogonadism
Causes of primary hypothyroidism
Autoimmune hypothyroidism Iatrogenic Drugs Congenital hypothyroidism Infiltrative disorders Goitrogens
