Hypothalamus and Pituitary Disorders Flashcards
How does the hypothalamus control the output from the anterior pituitary?
The hypothalamus releases hormones to stimulate output from the anterior pituitary.
How does the hypothalamus control the output from the posterior pituitary?
The hypothalamus controls the output of the posterior pituitary by direct nerve stimulation.
Which conditions increase the amount of ADH secreted per change in plasma osmolality?
Aging, hypercalcemia, hypoglycemia, and lithium treatment.
Which condition decreases the amount of ADH secreted per change in plasma osmolality?
Hypokalemia
Which conditions decrease the threshold for ADH secretion?
Pregnancy and pre-menses
Which conditions increase the threshold for ADH secretion?
Hypervolemia, acute HTN, and corticosteroids.
What physiologic states both increases the amount of ADH released and decreases the threshold for its release?
Volume contraction
What is the strongest osmolar stimulant of ADH osmoreceptors? Second strongest?
Sodium, then mannitol
What is the formula for determining plasma osmolality?
Osmolality = 2[Na+] + (glucose/18) + (BUN/2.8)
What is the most potent nonosmotic stimulant of ADH release?
Nausea. It can increase ADH to several hundred times the normal levels.
What is the osmolar threshold for triggering thirst?
Thirst is triggered when osmolality exceeds 295 mOsm/kg and increases in intensity with further elevation.
What are the six hormones secreted by the anterior pituitary?
GTAPP: Growth Hormone (GH), TSH, Adrenocorticotropic hormone (ACTH), Puberty (FSH and LH), and Prolactin.
Which two hormones are secreted by the posterior pituitary?
Oxytocin and ADH
Which two hypothalamic hormones control the release of Growth Hormone from the anterior pituitary?
Growth hormone releasing hormone (GHRH) stimulates GH release and Somatostatin inhibits its release.
Which two hypothalamic hormones control the release of TSH from the anterior pituitary?
TSH secretion is stimulated by the release of Thyrotropin-releasing hormone (TRH) and inhibited by the release of Somatostatin.
Which two hormones are inhibited by the release of Somatostatin?
Growth Hormone and TSH
What does ACTH stimulate the adrenal glands to produce?
It stimulates the adrenal glands to produce corticosteroids and androgens. It also has a permissive effect on the production of mineralocorticoids.
The release of which hypothalamic hormone stimulates the release of ACTH from the anterior pituitary?
Corticotropin-releasing hormone (CRH)
Which physiologic states will trigger the release of ACTH?
Physical or psychological stress stimulates the release of ACTH
What causes Cushing Disease?
Cushing Disease is caused by an ACTH-secreting pituitary tumor.
The production of which hormone is ultimately stimulated by the release of Serotonin?
Serotonin releases corticotropin-releasing hormone (CRH), which stimulates production of ACTH.
FSH and LH are produced in response to the secretion of which hypothalamic hormone?
The pulsatile secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus stimulates the production of FSH and LH from the anterior pituitary.
Which hormone inhibits FSH secretion and which organ releases it?
The gonads are the primary producer of inhibin, which acts to inhibit FSH secretion.
What regulates prolactin release?
Prolactin is under tonic hypothalamic inhibition by dopamine sent down the pituitary stalk. Prolactin increases during sleep and with stress, lactation, and stimulation of the nipple. It is also increased with antidopaminergic drugs (like metoclopramide and phenothiazines) and Thyrotropin-releasing hormone (TRH). Thus, prolactin increases with primary hypothyroidism and with any inhibition in the production of dopamine from the hypothalamus (most commonly caused by medications).
T/F: Prolactin levels are high in primary hypothyroidism.
TRUE
Which hormones are usually involved in congenital hypopituitarism?
Congenital hypopituitarism generally includes growth hormone deficiency, as well as ≥1 of the other 5 hormones produced in the anterior pituitary.
List six types of congenital defects which present with hypopituitarism.
Pallister-Hall syndrome, Rieger syndrome, Septooptic dysplasia, Midfacial anomalies, Empty sella, and Ectopic posterior pituitary.
Describe Pallister-Hall syndrome.
Pallister-Hall syndrome is the absence of the pituitary gland and is associated with hypothalamic hamartoblastoma, postaxial polydactyly, nail dysplasia, bifid epiglottis, imperforate anus, and heart, lung, and kidney anomalies.
Which syndrome is characterized by the absence of the pituitary gland and is associated with hypothalamic hamartoblastoma, postaxial polydactyly, nail dysplasia, bifid epiglottis, imperforate anus, and heart, lung, and kidney anomalies?
Pallister-Hall syndrome
Describe Rieger syndrome.
Rieger syndrome includes deficiency of anterior pituitary hormones, with the classic findings of colobomas of the iris, glaucoma, and kidney, GI, and/or umbilical anomalies.
Which syndrome includes deficiency of anterior pituitary hormones, with the classic findings of colobomas of the iris, glaucoma, and kidney, GI, and/or umbilical anomalies?
Rieger syndrome
What is septooptic dysplasia?
Septooptic dysplasia includes an abnormality of the optic nerve (absence of the optic chiasm, optic nerve hypoplasia, or both); agenesis or hypoplasia of the septum pellucidum or corpus callosum, or both; and often variable degrees of hypothalamic insufficienccy.
Which congenital disorder is characterized by an abnormality of the optic nerve (absence of the optic chiasm, optic nerve hypoplasia, or both); agenesis or hypoplasia of the septum pellucidum or corpus callosum, or both; and often variable degrees of hypothalamic insufficienccy?
Septooptic dysplasia
Which endocrine abnormality do you look for if a patient has a solitary maxillary central incisor?
There is a high likelihood of growth hormone deficiency in patients with a solitary maxillary central incisor.
Provide several examples of midfacial anomalies which can indicate the presence of hypopituitarism.
Patients with a solitary central maxillary incisor have a high likelihood of GH deficiency. Patients with cleft lip/cleft palate have about 4% chance of having GH deficiency. Bilateral or unilateral optic nerve hypoplasia is associated with hypopituitarism.
Describe the findings associated with empty sella.
Empty sella is a radiologic finding where the sella turcica, which usually holds the pituitary, is enlarged and appears empty.
What causes Empty sella?
Primary empty sella is probably due to a defect which allows CSF to fill the sella and flatten the pituitary. Secondary empty sella can be caused by previous surgery or radiation.
Which structure is key in determining the level of pituitary involvement in a patient with an ectopic posterior pituitary?
The pituitary stalk is key in determining the level of pituitary involvement. Patients who have an ectopic pituitary and a normal stalk have isolated GH deficiency. Patients with ectopic pituitary and an abnormal stalk tend to have multiple pituitary hormone deficiencies.
What types of pituitary deficiencies commonly occur with ectopic posterior pituitary?
Ectopic posterior pituitary can present with isolated GH deficiency or panhypopituitarism. Despite the fact that the ectopic tissue is from the posterior pituitary, deficiencies are most commonly anterior in origin.
What is the most common tumor to cause pituitary hormone deficiency?
Craniopharyngeoma, due to its location in the suprasellar region.
What are common presenting features of pituitary hormone deficiencies?
Growth failure, diabetes insipidus, and vision changes.
T/F: Infants with congenital growth hormone deficiency have normal length and weight at birth.
True
What are the clinical clues that make one suspect congenital GH deficiency?
Microphallus in males, hypoglycemia, and a prolonged direct hyperbilirubinemia in the neonatal period. They can also present early in life with neonatal apnea, cyanosis, or symptoms suggestive of sepsis.
What are the classic signs and symptoms of congenital GH deficiency?
Round head and short, broad face. The frontal bone is prominent and infants have a depressed, saddle-shaped nose. Eyes appear to bulge. They have high-pitched voices and small gonads. Facial, axillary, and pubic hair is sparse, if present at all. They have normal intelligence. (Add picture)
What features of a child’s growth curve should be concerning for possible growth hormone deficiency?
Postnatal growth failure (height or length > 3 SD below the mean) and slow growth velocity. Falling off the growth curve after 3 years of age is a huge red flag and deserves evaluation.
How does one definitively diagnose growth hormone deficiency?
Lack of response to growth hormone stimulation testing in the clinical setting of growth failure.
Add growth failure growth chart (Fig 15-1) to identify***