Hypothalamus and Pituitary Disorders Flashcards
1
Q
How does the hypothalamus control the output from the anterior pituitary?
A
The hypothalamus releases hormones to stimulate output from the anterior pituitary.
2
Q
How does the hypothalamus control the output from the posterior pituitary?
A
The hypothalamus controls the output of the posterior pituitary by direct nerve stimulation.
3
Q
Which conditions increase the amount of ADH secreted per change in plasma osmolality?
A
Aging, hypercalcemia, hypoglycemia, and lithium treatment.
4
Q
Which condition decreases the amount of ADH secreted per change in plasma osmolality?
A
Hypokalemia
5
Q
Which conditions decrease the threshold for ADH secretion?
A
Pregnancy and pre-menses
6
Q
Which conditions increase the threshold for ADH secretion?
A
Hypervolemia, acute HTN, and corticosteroids.
7
Q
What physiologic states both increases the amount of ADH released and decreases the threshold for its release?
A
Volume contraction
8
Q
What is the strongest osmolar stimulant of ADH osmoreceptors? Second strongest?
A
Sodium, then mannitol
9
Q
What is the formula for determining plasma osmolality?
A
Osmolality = 2[Na+] + (glucose/18) + (BUN/2.8)
10
Q
What is the most potent nonosmotic stimulant of ADH release?
A
Nausea. It can increase ADH to several hundred times the normal levels.
11
Q
What is the osmolar threshold for triggering thirst?
A
Thirst is triggered when osmolality exceeds 295 mOsm/kg and increases in intensity with further elevation.
12
Q
What are the six hormones secreted by the anterior pituitary?
A
GTAPP: Growth Hormone (GH), TSH, Adrenocorticotropic hormone (ACTH), Puberty (FSH and LH), and Prolactin.
13
Q
Which two hormones are secreted by the posterior pituitary?
A
Oxytocin and ADH
14
Q
Which two hypothalamic hormones control the release of Growth Hormone from the anterior pituitary?
A
Growth hormone releasing hormone (GHRH) stimulates GH release and Somatostatin inhibits its release.
15
Q
Which two hypothalamic hormones control the release of TSH from the anterior pituitary?
A
TSH secretion is stimulated by the release of Thyrotropin-releasing hormone (TRH) and inhibited by the release of Somatostatin.
16
Q
Which two hormones are inhibited by the release of Somatostatin?
A
Growth Hormone and TSH
17
Q
What does ACTH stimulate the adrenal glands to produce?
A
It stimulates the adrenal glands to produce corticosteroids and androgens. It also has a permissive effect on the production of mineralocorticoids.
18
Q
The release of which hypothalamic hormone stimulates the release of ACTH from the anterior pituitary?
A
Corticotropin-releasing hormone (CRH)
19
Q
Which physiologic states will trigger the release of ACTH?
A
Physical or psychological stress stimulates the release of ACTH
20
Q
What causes Cushing Disease?
A
Cushing Disease is caused by an ACTH-secreting pituitary tumor.
21
Q
The production of which hormone is ultimately stimulated by the release of Serotonin?
A
Serotonin releases corticotropin-releasing hormone (CRH), which stimulates production of ACTH.
22
Q
FSH and LH are produced in response to the secretion of which hypothalamic hormone?
A
The pulsatile secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus stimulates the production of FSH and LH from the anterior pituitary.
23
Q
Which hormone inhibits FSH secretion and which organ releases it?
A
The gonads are the primary producer of inhibin, which acts to inhibit FSH secretion.
24
Q
What regulates prolactin release?
A
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).
25
T/F: Prolactin levels are high in primary hypothyroidism.
TRUE
26
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.
27
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.
28
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.
29
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
30
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.
31
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
32
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.
33
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
34
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.
35
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.
36
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.
37
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.
38
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.
39
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.
40
What is the most common tumor to cause pituitary hormone deficiency?
Craniopharyngeoma, due to its location in the suprasellar region.
41
What are common presenting features of pituitary hormone deficiencies?
Growth failure, diabetes insipidus, and vision changes.
42
T/F: Infants with congenital growth hormone deficiency have normal length and weight at birth.
True
43
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.
44
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)
45
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.
46
How does one definitively diagnose growth hormone deficiency?
Lack of response to growth hormone stimulation testing in the clinical setting of growth failure.
47
Add growth failure growth chart (Fig 15-1) to identify***
***
48
Which labs should be performed in the workup of a patient presenting with short stature?
IGF-1, IGF-BP3, GH stim test if GH deficiency not ruled out with IGF results, CBC + diff, ESR or CRP, CMP, Celiac disease screen, TSH + free T4, urinalysis, karyotype (in girls).
49
When performing GH stimulation testing, what value is considered diagnostic of GH deficiency?
GH levels that do not rise above 10µg/L after stimulation using two different agents (false-negative results occur in ~20% of children if only one agent is used)
50
How are delayed and advanced bone ages diagnosed?
A bone age must be >2 SD from the mean to be considered delayed or advanced.
51
What is the typical bone age finding in patients with GH deficiency?
With GH deficiency, bone age is usually ~75% of chronologic age.
52
What is ideopathic short stature?
Patients with ideopathic short stature have height > 2.25 SD below the mean (1.2 percentile) and grow at a slower rate but have normal GH secretion.
53
T/F: Patients with ideopathic short stature can benefit from GH administration.
True. Patients with ISS who are treated with GH can have an increase in adult height of approximately 3.5-7.5cm (1.4-3.0 in).
54
What is Laron syndrome and how is it treated?
Laron syndrome is diagnosed in patients with short stature in spite of normal GH levels and is due to resistance to GH at the level of the GH receptor. They will have normal/high GH levels and low IGF-1 and IGF-BP3 levels. Laron syndrome should be treated with IGF-1 supplementation.
55
T/F: Children with constitutional growth delay typically require exogenous GH to reach their normal adult height.
False. Children with constitutional growth delay typically reach normal adult height without intervention.
56
Describe the typical pattern of growth in constitutional growth delay.
Normal growth occurs during the first 4-12 months of life, then slow so that height and weight are frequently less than the 3rd percentile. Normal growth velocity typically resumes by 2-3 years of age. These children often have delayed puberty.
57
Describe the typical bone age findings in patients with constitutional growth delay.
Bone age is delayed and mirrors height age rather than chronologic age.
58
Add constitutional growth delay growth chart (Fig 15-2) to identify***
***
59
Add genetic short stature growth chart (Fig 15-3) to identify***
***
60
Add growth hormone deficiency growth chart (Fig 15-4) to identify***
***
61
How would one distinguish between constitutional growth delay and familial short stature?
Familial short stature presents with normal growth velocity and growth that tracks at the predicted midparental height percentile. Bone age, if performed, would match chronologic age. In constitutional growth delay, the patient's growth would track below the predicet mid-parental height and they would have a delayed bone age.
62
What are the three major etiologies for short stature and what three tools are all that is needed to differentiate between them?
Constitutional growth delay, familial short stature, and growth hormone deficiency. Growth velocity, bone age, and family history is all that's needed to distinguish between them.
63
What are the typical growth velocity, bone age, and family history characteristics of constitutional growth delay?
Patients have a normal growth velocity in relation to their bone age, which is delayed. There is typically a family history of delayed puberty.
64
What are the typical growth velocity, bone age, and family history characteristics of familial short stature?
Patients have a normal growth velocity, a normal bone age, and a family history of short stature.
65
What are the typical growth velocity, bone age, and family history characteristics of GH deficiency?
Patients have a decreased growth velocity, delayed bone age, and occasional family history of hormone deficiency.
66
Draw out short stature summary table (Table 15-1).
***
67
Identify the etiology of this type of short stature: Patients have a normal growth velocity in relation to their bone age, which is delayed. There is typically a family history of delayed puberty.
Constitutional growth delay
68
Identify the etiology of this type of short stature: Patients have a normal growth velocity, a normal bone age, and a family history of short stature.
Familial short stature
69
Identify the etiology of this type of short stature: Patients have a decreased growth velocity, delayed bone age, and occasional family history of short stature.
Growth hormone deficiency
70
What is the midparental height calculation for males?
(Mom's height + Dad's height + 13 cm)/2
71
What is the midparental height calculation for females?
(Mom's height + Dad's height - 13 cm)/2
72
What is Russell-Silver Syndrome?
Russel-Silver syndrome causes short stature, frontal bossing, triangular facies, shortened and incurved 5th fingers (clinodactyly), and asymmetry. They have low birthweights (SGA) and failure to thrive. ***insert picture
73
Describe the typical therapy course for patients with classic GH deficiency.
Begin treatment as soon as a diagnosis is confirmed with recombinant human GH at a dose of 0.18-0.30 mg/kg/week, subcutaneously, in 6-7 divided doses per week. Continue until the child reaches adult height, typically once bone age is >14 years for girls and >16 years in boys.
74
While treating with GH, which side effects should be monitored at each visit?
Slipped capital femoral epiphysis (SCFE), pseudotumor cerebri, transient carbohydrate intolerance, transient hypothyroidism, and scoliosis.
75
Which children with short stature are FDA approved to receive GH to help them reach a more normal height?
Patients with GH deficiency, ideopathic short stature, chronic renal insufficiency, Turner syndrome, Prader-Willi syndrome, SGA if not caught up by 2 years of age, Noonan syndrome, AIDS-wasting syndrome, and SHOX (short stature homeobox) gene deletion.
76
What study should be performed before starting patients with Prader-Willi on GH therapy?
They should have a sleep study to evaluate for sleep apnea prior to starting GH therapy.
77
What are the classic presenting symptoms for diabetes insipidus?
Polyuria and polydipsia.
78
What is the underlying etiology for central diabetes insipidus?
Central DI occurs because of problems with synthesis and/or secretion of vasopressin (aka ADH).
79
What is the underlying etiology for nephrogenic diabetes insipidus?
Nephrogenic DI is due to the lack of response to ADH by the kidney's collecting tubules.
80
ADH receptors are located throughout the body, but where is their key site?
The collecting duct of the nephron. Without ADH, the collecting ducts exhibit extremely low water permeability, causing the body to lose water in large volumes as dilute urine (typically <200mOsm/kg).
81
List three rare inherited forms of central diabetes insipidus.
Autosomal dominant central DI, Wolfram syndrome, and septooptic dysplasia.
82
What are some secondary/acquired forms of central diabetes insipidus?
Tumors (craniopharyngioma, optic glioma, germinoma), head injury, idiopathic, neurologic procedures that damage the hypothalamus, pituitary, or pituitary stalk, and certain diseases (sarcoidosis, encephalitis, langerhans cell histiocytosis, tuberculosis).
83
Include figures 15-5 and 15-6 to visualize central/nephrogenic DI
***
84
What is the most common medication to cause nephrogenic DI?
Lithium
85
Which disorders can cause nephrogenic diabetes insipidus?
Polycystic kidney disorder, sickle cell disease, chronic pyelonephritis, sarcoidosis, amyloidosis, and urinary tract obstructions.
86
What are the plasma and urine osmolalities considered to be pathognomonic for diabetes insipidus?
A plasma osmolality >300 mOsm/kg with a urine osmolality <300 mOsm/kg is pathognomonic for DI.
87
What is the treatment for central diabetes insipidus?
Central DI responds very well to desmopressin (DDAVP) given orally or intranasally in a single or divided dose. The typical starting dose is 0.05-0.10 mg orally or 5-10µg intranasally.
88
What is the treatment for nephrogenic diabetes insipidus?
Discontinue drugs which may be causing the DI. Initiate a low sodium diet and adequate water intake (300-400 ml/kg/day). Pharmacologic agents may be used as well: Thiazides and prostaglandin synthesis inhibitors reduce urine output and Amiloride is especially useful in lithium-induced DI.
89
Describe the pathology of SIADH (syndrome of inappropriate ADH secretion).
SIADH causes increased collecting duct permeability to water with resulting hypervolemia and low plasma osmolality with dilutional hyponatremia.
90
Describe the expected urine characteristics in SIADH.
Urine is low in volume and extremely concentrated.
91
What are the most common factors leading to increased secretion of ADH?
Pain, pneumonia, tumors, tuberculosis, cystic fibrosis, meningitis, encephalitis, head trauma, and neurosurgical procedures.
92
Which antineoplastic agents are associated with the development of SIADH?
Vincristine and vinblastine
93
A child with severe head injury 3 days ago now has severe hyponatremia; what is one etiology you should consider?
SIADH
94
How is SIADH best managed?
Treat SIADH with fluid restriction. Also treat the underlying etiology if known. The antibiotic demeclocycline interferes with the ADH receptor and can be used in patients with chronic hyponatremia due to SIADH.
95
Describe the typical presentation of a patient with cerebral salt wasting.
Cerebral salt wasting is typically seen in patients with CNS disorders (brain tumors, head trauma, hyddrocephalus, and cerebral vascular accidents). They typically present with increased urine output and resultant hypovolemia. They will have hyponatremia, increased sodium excretion in the urine, low vasopressin/ADH, and high atrial natriuretic peptide (ANP) levels.
96
Compare/contrast lab values in cerebral salt wasting with those found in SIADH.
In patients with cerebral salt wasting, labs reveal low plasma sodium, high urinary sodium excretion, low vasopressin/ADH, and high ANP concentrations. In patients with SIADH, patients have low urine output, low plasma sodium, high vasopressin/ADH, and normal ANP concentrations.
97
What is the typical physiologic role for atrial natriuretic peptide (ANP)?
ANP is normally released in response to hypervolemic states. It promotes salt and water excretion and lowers blood pressure.
98
What is recommended management for cerebral salt wasting?
Replace urine output with IV fluids (NS to 3% saline), then transition to oral sodium replacement once the patient can tolerate PO medications.
99
How do lab values differ in SIADH vs ACTH-adrenal-cortisol axis deficiency?
ACTH-adrenal-cortisol axis deficiency presents with dilute urine, low urine osmolality, hypoglycemia, and normokalemia. In contrast, SIADH has low urine output and high urine osmolality. They both cause hyponatremia.
100
Which is more common in childhood - primary or secondary hyperpituitarism?
Secondary hyperpituitarism is much more common than primary and is always caused by a deficiency of the target hormone (i.e. if the thyroid gland isn't producing T3/T4, the result is an overproduction of TSH).
101
What is the definition of tall stature?
Tall stature is defined as being >2 SD above the mean height for age.
102
Name three abnormal genetic causes of tall stature.
Klinefelter syndrome (XXY), Marfan syndrome (autosomal dominant), and homocystinuria (autosomal recessive).
103
What should be the initial workup for a child in whom you suspect pathologic tall stature?
Screen for GH excess with a random GH level, serum IGF-1 concentration, and serum IGF-BP3 concentration. If there is increased GH, order a brain/sella MRI. If Klinefelter is suspected, a karyotype should also be sent.
104
How does one differentiate between homocystinuria and Marfan syndrome?
Both have tall stature, but Marfan's is autosomal dominant with upward lens subluxation and normal intelligence. In patients with homocystinuria, incidence is low (autosomal recessive), IQ is low (intellectual disability), and lenses are low (sublux downward).
105
Which sex hormone is responsible for fusing the growth plates?
Estrogen. If attempting to limit growth in patients with pathologic tall stature, estrogen would be administered to girls early in puberty and testosterone would be administered to boys (the body converts the testosterone to estrogen).
106
Which hormone is responsible for overgrowth in overgrowth syndromes?
Overgrowth is caused by an excess of IGF-2
107
What is Beckwith-Wiedemann syndrome?
Beckwith-Wiedemann syndrome is an overgrowth disorder caused by imprinting. These patients present at birth with macroglossia, hepatosplenomegaly, nephromegaly, and pancreatic β-cell hyperplasia which causes hyperinsulinemia and resultant hypoglycemia. These patients are predisposed to the development of Wilms tumor, adrenocortical carcinoma, and hepatoblastoma.
108
What is the underlying genetic abnormality associated with Beckwith-Wiedemann syndrome?
Most cases are due to paternal deletion of 15q11-13 but it can also be caused by maternal uniparental disomy.
109
What oncologic disorders are common in patients with Beckwith-Wiedemann syndrome and what is the recommended screening?
Wilms tumor, adrenocortical carcinoma, and hepatoblastoma. These patients should have an abdominal ultrasound every 3 months until 8 years of age and an alpha-fetoprotein every 6 weeks until 6 years of age.
110
What condition is caused by the presence of a GH-producing pituitary adenoma in the setting of open epiphyses?
Gigantism. If the epiphyses are closed, the excess of GH will cause acromegaly.
111
What are the typical physical and laboratory changes resulting from GH-producing pituitary adenomas in children with open epiphyses?
The child will have rapid linear growth, coarse facies, and enlarging hands and feet. Delayed sexual maturation/hypogonadism is common. Labs reveal high GH levels, usually >400 ng/mL. MRI will typically show the adenoma.
112
Patients with which two disorders are at excess risk for the development of GH excess?
McCune-Albright syndrome and Carney complex
113
What are some of the treatment options for GH excess?
Surgery to remove the adenoma, radiation therapy, or medications. Medications include somatostatin analogues such as octreotide and lanreotide (used to shrink the adenoma), Pegvisomant is a GH receptor antagonist that can lower the effect of elevated GH levels and is used when somatostatin analogue therapy is insufficient.
114
What is Sotos syndrome?
AKA Cerebral gigantism. This presents with rapid growth in early childhood but without any evidence for an underlying endocrine disorder. Affected infants are born above the 90th percentile and grow rapidly in the first year of life to >97th percentile. Accelerated growth persists until 4-5 years of age and then normalizes. Puberty occurs at normal time or slightly early (appropriate for slightly advanced bone age). These children have large hands and feet and present as clumsy. They have some degree of intellectual disability. Most achieve normal adult heights.
115
What is the most common anterior-pituitary tumor in adolescents?
Prolactinoma
116
How might an adolescent female present with prolactinoma?
Symptoms generally include headache, amenorrhea, and galactorrhea.
117
What is the best way to diagnose a prolactinoma?
MRI of the sella is the best diagnostic tool.
118
How is prolactinoma treated?
Cabergoline and bromocriptine are the drugs of choice and decrease both the size and the secretion of the prolactinoma. Cabergoline is more effective and better tolerated than bromocriptine. If drug therapy fails, surgical resection is indicated using the transfrontal or transsphenoidal approach.
