Phosphate Disorders Hypophosphatemia Flashcards
(222 cards)
1
Q
What is hypophosphatemia defined as?
A
Serum phosphorus level [Pi] < 2.5 mg/dL
2
Q
What are the highest and lowest serum phosphorus levels observed during the day in individuals with normal kidney function?
A
Highest in the early morning hours, lowest in the late morning hours
3
Q
What condition develops in patients receiving mannitol?
A
Pseudohypophosphatemia
4
Q
What causes pseudohypophosphatemia in patients receiving mannitol?
A
Binding of mannitol to the molybdate used to determine the serum [Pi]
5
Q
What are the classifications of hypophosphatemia based on serum [Pi] levels?
A
- Severe: [Pi] < 1.0 mg/dL
- Moderate: [Pi] 1.0–1.9 mg/dL
- Mild: [Pi] 2.0–2.5 mg/dL
6
Q
In which patients is hypophosphatemia commonly seen?
A
Hospitalized patients with sepsis, chronic alcoholism, COPD, and trauma
7
Q
What are the four categories of causes of hypophosphatemia?
A
- Shift from extracellular to intracellular compartment
- Decreased intestinal absorption
- Increased kidney loss
- Drugs
8
Q
What is one mechanism that causes hypophosphatemia due to a shift from extracellular to intracellular compartment?
A
Glucose-induced transcellular distribution
9
Q
What role do phosphate binders play in hypophosphatemia?
A
They bind phosphate in the gut, decreasing intestinal absorption
10
Q
Which vitamin deficiency is associated with decreased intestinal absorption leading to hypophosphatemia?
A
Vitamin D deficiency
11
Q
What is the effect of primary and secondary hyperparathyroidism on kidney phosphate absorption?
A
Decreases kidney absorption by inhibiting phosphate transporters
12
Q
What is the most common hypophosphatemic disorder?
A
X-Linked Hypophosphatemia
13
Q
What gene is mutated in X-Linked Hypophosphatemia?
A
PHEX gene
14
Q
What are the clinical features of X-Linked Hypophosphatemia?
A
- Hypophosphatemia
- Phosphaturia
- Short stature
- Rickets and osteomalacia
- Dental abscesses
15
Q
What is the treatment for X-Linked Hypophosphatemia?
A
Oral calcitriol and phosphate
16
Q
What causes Autosomal Dominant Hypophosphatemic Rickets (ADHR)?
A
Activating mutations in the FGF-23 gene
17
Q
What are common symptoms of ADHR?
A
- Hypophosphatemia
- Lower extremity deformities
- Bone pain
- Weakness
- Phosphaturia
18
Q
What is the treatment for Autosomal Recessive Hypophosphatemic Rickets (ARHR)?
A
Calcitriol and phosphate
19
Q
What is Tumor-Induced Osteomalacia (TIO)?
A
An acquired paraneoplastic syndrome associated with mesenchymal tumors
20
Q
What are the biochemical findings in Tumor-Induced Osteomalacia?
A
- Phosphaturia
- Elevated FGF-23
- Normal Ca²⁺ and PTH levels
21
Q
What is the treatment strategy for Tumor-Induced Osteomalacia?
A
Identification and resection of the tumor, calcitriol, and phosphate
22
Q
What characterizes Hereditary Hypophosphatemic Rickets with Hypercalciuria due to Type IIc mutations?
A
Mutations in the Na/Pi-type IIc cotransporter gene
23
Q
What is the predominant treatment for Hereditary Hypophosphatemic Rickets with Hypercalciuria?
A
Phosphate supplementation
24
Q
What is the genetic cause of Hereditary Hypophosphatemic Rickets with Hypercalciuria due to Type IIa mutations?
A
Heterozygous mutations in the SLC34A1 gene
25
What is the role of Na/H Exchanger Regulatory Factor (NHERF)1 in phosphate transport?
Maintains stability of Na/Pi-IIc cotransporter at the apical membrane
26
What is the effect of mutations in the NHERF1 gene?
Causes hypophosphatemia, phosphate wasting, and increased risk for kidney stones
27
What are common treatments for various hypophosphatemic conditions?
* Calcitriol
* Phosphate supplementation
28
True or False: Hypophosphatemia is common in the general population.
False
29
What is the genetic mutation associated with X-linked hypophosphatemia (XLH)?
PHEX gene mutation
## Footnote
XLH is characterized by elevated FGF-23 levels and low phosphate levels.
30
What is the effect of FGF-23 in hypophosphatemic disorders?
Increased phosphate excretion and decreased serum phosphate
## Footnote
FGF-23 plays a key role in phosphate regulation.
31
Which disorder is associated with a mutation in the DMP1 gene?
Autosomal recessive hypophosphatemic rickets type 1 (ARHR1)
## Footnote
ARHR1 shows increased FGF-23 and decreased phosphate levels.
32
What is the most common electrolyte abnormality observed in refeeding syndrome (RFS)?
Hypophosphatemia
## Footnote
RFS occurs in malnourished individuals after nutrition is restarted.
33
What are the mechanisms contributing to hypophosphatemia in refeeding syndrome?
High carbohydrate meals, increased glycolysis, depleted phosphate stores, phosphate consumption for ATP
## Footnote
Each mechanism contributes to the shift and depletion of phosphate.
34
True or False: Hypophosphatemia can lead to sudden deaths in refeeding syndrome.
True
## Footnote
High caloric diets can exacerbate hypophosphatemia, leading to organ failure.
35
What is the typical serum phosphate level in acute severe symptomatic hypophosphatemia?
<1.0 mg/dL
## Footnote
This condition requires careful monitoring and treatment.
36
What is the recommended initial treatment for severe hypophosphatemia?
IV phosphate administration
## Footnote
Oral phosphate is preferred when symptoms are absent.
37
List the main clinical manifestations of severe hypophosphatemia.
* Neurologic: confusion, seizures
* Cardiovascular: cardiomyopathy
* Skeletal muscle: weakness, rhabdomyolysis
* Bone: pain, rickets
* Hematologic: hemolysis
* Respiratory: muscle weakness, hypoxia
## Footnote
These manifestations result from ATP depletion and altered cellular function.
38
What is the role of cinacalcet in kidney transplantation?
Improves PTH levels and phosphate wasting
## Footnote
This treatment addresses secondary hyperparathyroidism post-transplant.
39
What laboratory findings are indicative of kidney phosphate wasting?
FEₚₒ₄ >5%
## Footnote
This indicates that the kidneys are losing phosphate and not absorbing it.
40
What is the normal range for TmP/GFR in adults?
0.8–1.35 mmol/L
## Footnote
Values <0.8 indicate kidney phosphate wasting.
41
What is the first step in diagnosing hypophosphatemia?
Establish the cause through history and physical examination
## Footnote
This involves looking for signs and symptoms as well as dietary and medication history.
42
Fill in the blank: The presence of _______ can indicate chronic alcoholism in a patient with hypophosphatemia.
Hepatomegaly
## Footnote
This can be a sign of underlying causes contributing to phosphate deficiency.
43
What are the potential risks of IV phosphate administration?
Hypocalcemia and fluid overload
## Footnote
Patients with heart failure are particularly at risk.
44
What is a common cause of hypophosphatemia in critically ill patients?
Use of glucose-containing solutions
## Footnote
This can lead to shifts in phosphate levels.
45
What is the relationship between ATP depletion and hypophosphatemia?
Depletion of ATP leads to altered cellular function and hypoxia
## Footnote
ATP is critical for energy metabolism and cellular functions.
46
What should be monitored in patients receiving IV phosphate repletion?
Serum phosphate levels
## Footnote
Frequent monitoring is crucial to avoid complications.
47
What is the biochemical abnormality associated with decreased 2,3-diphosphoglycerate in hypophosphatemia?
Increased oxygen affinity of hemoglobin
## Footnote
This can lead to reduced oxygen delivery to tissues.
48
Name a treatment for hypophosphatemia that can be given orally.
Neutra-phos
## Footnote
This is a common oral phosphate preparation.
49
What is the serum phosphate level range for moderate hypophosphatemia?
0.58–0.7 mmol/L (1.8–2.2 mg/dL)
50
What complications are associated with IV phosphate administration?
Hypocalcemia and hyperphosphatemia
51
When is IV phosphate administration generally not required?
In moderate hypophosphatemia unless symptoms warrant IV therapy
52
What is the management approach for chronic hypophosphatemia?
Depends on the underlying cause; oral therapy is indicated
53
What can long-term oral therapy for hypophosphatemia suppress?
1,25(OH)₂D₃ levels and raise PTH and FGF-23 levels
54
What is suggested to suppress PTH levels in chronic hypophosphatemia?
Concomitant administration of calcitriol
55
What dietary change may improve hypophosphatemia in kidney transplant patients?
Increase in dietary phosphate
56
What is a major concern when using oral phosphate therapy in severe hypophosphatemia?
Hyperphosphatemia
57
Which drug does NOT cause hypophosphatemia?
Calcitriol
58
What is the serum phosphate level for severe hypophosphatemia?
<1.0 mg/dL
59
Which metabolic abnormality is NOT related to severe hypophosphatemia?
Metabolic alkalosis
60
What is a complication of low serum phosphate levels?
Rhabdomyolysis
61
What treatment is indicated for asymptomatic moderate hypophosphatemia?
Oral phosphate repletion
62
What is the treatment for hyperalimentation-induced severe hypophosphatemia?
Aggressive intravenous (IV) treatment with 1 mmol/kg over 10 h
63
What does transcellular distribution of phosphate occur after?
Carbohydrate load or glucose infusion
64
Which human phosphate wasting disease is associated with high levels of active vitamin D?
Primary hyperparathyroidism
65
What is the serum phosphate status in Autosomal Dominant Hypophosphatemic Rickets (ADHR)?
↓
66
What is the serum calcium status in Autosomal Recessive Hypophosphatemic Rickets (ARHR)?
N
67
What is the serum 1,25(OH)₂D₃ level in X-linked hypophosphatemia (XLH)?
↓/N
68
What is the PTH status in tumor-induced osteomalacia (TIO)?
N
69
Match the serum values with the patient history: A 45-year-old woman with hilar adenopathy
A
70
Match the serum values with the patient history: A 30-year-old obese female with short-bowl resection
B
71
Match the serum values with the patient history: A 60-year-old man with a lung mass
C
72
Match the serum values with the patient history: A 24-year-old female with flank pain and UTIs
D
73
Match the serum values with the patient history: A 50-year-old housewife with joint pain and nocturia
E
74
What is hypophosphatemia defined as?
A serum phosphorus level [Pi] < 2.5 mg/dL
75
When are the highest serum phosphorus levels typically observed?
In the early morning hours
76
What condition can develop in patients receiving mannitol?
Pseudohypophosphatemia
77
What causes pseudohypophosphatemia in patients receiving mannitol?
Binding of mannitol to the molybdate used to determine serum [Pi]
78
What leukocyte count can cause pseudohypophosphatemia?
Leukocyte count >310,000/μL
79
How can pseudohypophosphatemia be corrected?
Filtration of serum deproteinizes
80
What are the three classifications of hypophosphatemia based on severity?
* Severe: serum [Pi] < 1.0 mg/dL
* Moderate: serum [Pi] 1.0–1.9 mg/dL
* Mild: serum [Pi] 2.0–2.5 mg/dL
81
What can cause severe hypophosphatemia?
Prolonged use of antacids such as aluminum hydroxide, magnesium hydroxide, or calcium carbonate/acetate
82
Is moderate hypophosphatemia typically symptomatic or asymptomatic?
May be symptomatic or asymptomatic
83
Is hypophosphatemia common in the general population?
No, it is rather uncommon
84
What conditions have a high incidence of hypophosphatemia in hospitalized patients?
* Sepsis
* Chronic alcoholism
* Chronic obstructive pulmonary disease (COPD)
85
What type of patients also have a high incidence of hypophosphatemia?
Patients with trauma
86
What is one cause of hypophosphatemia related to the shift of phosphate?
Shift from extracellular to intracellular compartment
## Footnote
This includes factors such as glucose, insulin, catecholamines, and respiratory alkalosis.
87
What mechanism does insulin use to contribute to hypophosphatemia?
Transcellular distribution
## Footnote
Insulin facilitates the movement of phosphate from the extracellular to the intracellular compartment.
88
What is refeeding syndrome in relation to hypophosphatemia?
Glucose and insulin-induced transcellular distribution, consumption during glucose metabolism, and ATP production
## Footnote
This condition can lead to significant phosphate depletion.
89
What is one cause of hypophosphatemia due to decreased intestinal absorption?
Malabsorption
## Footnote
This results in reduced intestinal absorption of phosphate.
90
What do phosphate binders do?
Bind phosphate in the gut
## Footnote
Examples include calcium acetate, aluminum hydroxide, and magnesium salts.
91
What is Tenapanor's role in hypophosphatemia?
Na/H exchanger isoform 3 inhibitor, which reduces paracellular transport of phosphate in the intestine
## Footnote
It helps in managing phosphate levels by affecting intestinal absorption.
92
What is a consequence of vitamin D deficiency in relation to hypophosphatemia?
Decreased intestinal absorption
## Footnote
Vitamin D is crucial for phosphate absorption in the intestines.
93
What can lead to increased kidney loss of phosphate?
Primary and secondary hyperparathyroidism
## Footnote
These conditions inhibit phosphate transporters in the proximal tubule.
94
What genetic condition is associated with mutations in the PHEX gene?
X-linked hypophosphatemia
## Footnote
This inherited disorder results in phosphate wasting.
95
What is one drug that can cause hypophosphatemia?
Osmotic diuretics
## Footnote
These decrease kidney reabsorption and increase phosphaturia.
96
What effect do corticosteroids have on phosphate levels?
Decrease intestinal phosphate absorption and increase phosphaturia
## Footnote
This can contribute to hypophosphatemia.
97
Fill in the blank: Alcoholism can lead to hypophosphatemia due to _______.
Poor intake, frequent use of phosphate binders, vitamin D deficiency
## Footnote
Alcoholism can significantly impact phosphate levels through various mechanisms.
98
What is the effect of diabetic ketoacidosis on phosphate levels?
Decreased total body phosphate due to osmotic diuresis
## Footnote
Hypophosphatemia can occur after insulin administration.
99
True or False: Metabolic acidosis decreases Na/Pi-IIa cotransporter activity.
True
## Footnote
This can result in lower phosphate reabsorption in the kidneys.
100
What is a potential consequence of toxic shock syndrome related to phosphate?
Cellular uptake probably due to respiratory alkalosis
## Footnote
This condition can lead to hypophosphatemia through altered cellular mechanisms.
101
102
What is the most common hypophosphatemic disorder?
X-Linked Hypophosphatemia
## Footnote
Inherited as an autosomal dominant disease
103
What gene is associated with X-Linked Hypophosphatemia?
PHEX (phosphate-regulating gene with homologies to endopeptidases on the X chromosome)
## Footnote
Inactivating mutations in this gene cause the disorder
104
At what age does X-Linked Hypophosphatemia typically present?
Within 2 years of age
105
List the key characteristics of X-Linked Hypophosphatemia.
* Hypophosphatemia
* Phosphaturia
* Short stature
* Rickets and osteomalacia
* Dental abscesses
106
What are the effects of X-Linked Hypophosphatemia on calcium and phosphate absorption?
Decreased intestinal Ca²⁺ and phosphate absorption, and decreased kidney phosphate absorption
107
What is the role of FGF-23 in X-Linked Hypophosphatemia?
It is produced due to inactivating mutations of PHEX
108
What are the biochemical characteristics of X-Linked Hypophosphatemia?
* Elevated FGF-23 levels
* Normal serum Ca²⁺ levels
* Normal parathyroid hormone (PTH) levels
* Low 1,25(OH)₂D₃ levels
109
How does high FGF-23 activity affect vitamin D levels in X-Linked Hypophosphatemia?
It leads to low 1,25(OH)₂D₃ levels
110
What treatment options are available for X-Linked Hypophosphatemia?
* Oral calcitriol
* Phosphate
* Burosumab (human anti-FGF23 monoclonal antibody)
111
True or False: Treatment with oral calcitriol and phosphate reduces phosphaturia.
False
112
What is the effectiveness of burosumab in treating X-Linked Hypophosphatemia?
It appears to be effective in children 1 year and older
113
What is the most common hypophosphatemic disorder?
X-Linked Hypophosphatemia
## Footnote
Inherited as an autosomal dominant disease
114
What gene is associated with X-Linked Hypophosphatemia?
PHEX (phosphate-regulating gene with homologies to endopeptidases on the X chromosome)
## Footnote
Inactivating mutations in this gene cause the disorder
115
At what age does X-Linked Hypophosphatemia typically present?
Within 2 years of age
116
List the key characteristics of X-Linked Hypophosphatemia.
* Hypophosphatemia
* Phosphaturia
* Short stature
* Rickets and osteomalacia
* Dental abscesses
117
What are the effects of X-Linked Hypophosphatemia on calcium and phosphate absorption?
Decreased intestinal Ca²⁺ and phosphate absorption, and decreased kidney phosphate absorption
118
What is the role of FGF-23 in X-Linked Hypophosphatemia?
It is produced due to inactivating mutations of PHEX
119
What are the biochemical characteristics of X-Linked Hypophosphatemia?
* Elevated FGF-23 levels
* Normal serum Ca²⁺ levels
* Normal parathyroid hormone (PTH) levels
* Low 1,25(OH)₂D₃ levels
120
How does high FGF-23 activity affect vitamin D levels in X-Linked Hypophosphatemia?
It leads to low 1,25(OH)₂D₃ levels
121
What treatment options are available for X-Linked Hypophosphatemia?
* Oral calcitriol
* Phosphate
* Burosumab (human anti-FGF23 monoclonal antibody)
122
True or False: Treatment with oral calcitriol and phosphate reduces phosphaturia.
False
123
What is the effectiveness of burosumab in treating X-Linked Hypophosphatemia?
It appears to be effective in children 1 year and older
124
What is Autosomal Dominant Hypophosphatemic Rickets (ADHR)?
ADHR is a rare disorder caused by activating mutations in the FGF-23 gene, preventing proteolytic cleavage of FGF-23 and increasing circulating levels of this hormone.
125
What is the phenotype of ADHR similar to?
The phenotype is similar to that of X-linked hypophosphatemia.
126
What is the clinical onset variability in ADHR due to?
Incomplete penetrance.
127
How does ADHR typically present in childhood?
Hypophosphatemia and lower extremity deformities.
128
What symptoms may develop in adolescence or adulthood for individuals with ADHR?
Bone pain, weakness, and phosphaturia.
129
What may happen to phosphaturia in some ADHR patients after puberty?
It may improve.
130
What is the treatment for ADHR?
Calcitriol and phosphate.
131
What causes Autosomal Recessive Hypophosphatemic Rickets type 1 (ARHR1)?
Inactivating mutations in the DMP (dentin matrix protein) 1 gene.
132
What role does DMP 1 play in the body?
Participates in bone mineralization of extracellular matrix.
133
What is the clinical manifestation of DMP 1 deficiency similar to?
Similar to that of ADHR.
134
What causes Autosomal Recessive Hypophosphatemic Rickets type 2 (ARHR2)?
Inactivating mutation in the ENPPI (endonucleotide pyrophosphatase/phosphodiesterase I) gene.
135
What is the treatment for both ARHR1 and ARHR2?
Calcitriol and phosphate.
136
What does TIO stand for?
Tumor-Induced Osteomalacia
137
What type of tumors are typically associated with TIO?
Mesenchymal tumors
138
During which decade of life does TIO usually occur?
6th decade of life
139
Name one phosphaturic factor associated with TIO.
FGF-23
140
List three other phosphaturic factors identified with TIO.
* sFRP-4 (frizzled-related protein-4)
* MEPE (matrix extracellular phosphoryloprotein)
* FGF-7
141
What are the biochemical findings in TIO similar to?
ADHR
142
What are the biochemical markers associated with TIO?
* Phosphaturia
* Elevated FGF-23
* Normal Ca²⁺ levels
* Normal PTH levels
143
What is the first step in the treatment of TIO?
Identification of the tumor
144
What treatments are included for TIO?
* Resection or chemotherapy
* Calcitriol
* Phosphate
145
What is Hereditary Hypophosphatemic Rickets with Hypercalciuria (HHRH) caused by?
Mutations in the gene that encodes Na/Pi-type IIc cotransporter
## Footnote
It is a rare autosomal recessive disorder.
146
At what age does HHRH typically occur?
In the first 2 years of life.
147
What are the main clinical features of HHRH?
* Growth retardation
* Rickets
* Increased kidney phosphate and Ca²⁺ excretion
148
How does HHRH differ from other hypophosphatemic rickets?
HHRH is characterized by elevated levels of 1,25(OH)₂D₃, leading to hypercalciuria and hypercalcemia.
149
What is the recommended treatment for HHRH?
Phosphate supplementation.
150
Is calcitriol recommended for treating HHRH?
No, it is not recommended due to the risk of hypercalcemia and kidney stone formation.
151
What gene is associated with Type IIa mutations in hereditary hypophosphatemic rickets?
SLC34A1 gene (Na/Pi-IIa protein).
152
What biochemical abnormalities were reported in patients with Type IIa mutations?
* Hypophosphatemia
* Phosphate wasting
* Elevated 1,25(OH)₂D₃ levels
153
What was discovered in the study of siblings with Type IIa mutations after 20 years?
Persistent Fanconi syndrome, phosphate wasting, bone mineral deficiency, and decreased glomerular filtration rates.
154
What is the role of Na/H Exchanger Regulatory Factor (NHERF)1 in phosphate transport?
It maintains the stability of the Na/Pi-II₆ cotransporter at the apical membrane.
155
What condition was found in individuals with loss-of-function mutations in the NHERF1 gene?
Hypophosphatemia and phosphate wasting with higher risk for kidney stones and bone demineralization.
156
What did Schlingmann et al. report regarding SCL34A1 mutations?
Loss-of-function mutations in SCL34A1 in infants with idiopathic infantile hypercalcemia and nephrolithiasis.
157
What were the clinical features of the case of hypophosphatemic rickets in a 13-month-old girl with Klotho mutation?
* Poor linear growth
* Large head
* Poor response to vitamin D₂ therapy
158
What genetic abnormality was found in the girl with hypophosphatemic rickets related to Klotho?
A de novo translocation of the α-Klotho gene.
159
How did the girl's condition improve?
With vitamin D₂ and phosphate treatment.
160
What was the result of the girl's treatment by age 7?
She developed hypercalcemia, requiring parathyroidectomy.
161
What gene is associated with X-linked hypophosphatemia (XLH)?
PHEX
## Footnote
XLH is characterized by elevated FGF-23 and decreased phosphate (Pi) levels.
162
What is the FGF-23 level in autosomal dominant hypophosphatemic rickets (ADHR)?
↑
## Footnote
ADHR is associated with the FGF-23 gene.
163
In what disorder is DMP1 the associated gene?
ARHR1
## Footnote
ARHR1 features elevated FGF-23 and decreased phosphate levels.
164
What gene is linked to ARHR2?
ENPP1
## Footnote
Similar to ARHR1, ARHR2 also has elevated FGF-23 and decreased phosphate.
165
What is the calcitriol level in hereditary hypophosphatemic rickets with hypercalciuria (HHRH) associated with SLC34A3?
↑
## Footnote
This form of HHRH shows decreased phosphate levels and increased calcium excretion.
166
Which gene is associated with the HHRH condition that has N for FGF-23?
SLC34A1
## Footnote
This variant of HHRH shows increased phosphate and calcium excretion.
167
What is the phosphate excretion level in NHERF1 disorder?
N
## Footnote
NHERF1 shows elevated calcitriol and increased calcium excretion.
168
What is the calcium level in Klotho disorder?
↓
## Footnote
Klotho disorder features elevated FGF-23 and PTH levels.
169
Fill in the blank: The phosphate (Pi) level in XLH is _______.
↓
## Footnote
XLH is characterized by elevated FGF-23 and normal PTH levels.
170
True or False: In HHRH with SLC34A3, the phosphate excretion is decreased.
False
## Footnote
HHRH with SLC34A3 shows increased phosphate excretion.
171
What is the PTH level in ARHR1?
N
## Footnote
ARHR1 features elevated FGF-23 and decreased phosphate levels.
172
What is Refeeding Syndrome (RFS)?
RFS occurs in malnourished individuals following administration of oral, enteral, or parenteral nutrition.
## Footnote
Commonly seen in hospitalized patients who are malnourished due to poor oral intake, starvation, anorexia nervosa, or systemic illness such as malignancy.
173
What is the most commonly observed electrolyte abnormality induced by RFS?
Hypophosphatemia.
## Footnote
This condition is characterized by low levels of phosphate in the blood.
174
What are some mechanisms that contribute to hypophosphatemia in RFS?
* High carbohydrate meal causing intracellular shift of phosphate
* Increased consumption of phosphate during glycolysis
* Depleted body stores of phosphate during poor oral intake
* Consumption of phosphate for formation of ATP and increased production of products such as creatine kinase and 2,3-diphosphoglycerate.
## Footnote
These mechanisms lead to a rapid decrease in phosphate availability in the body.
175
What severe consequence can occur following RFS with a high caloric diet?
Sudden deaths due to hypophosphatemia, leading to almost all organ systems failing.
## Footnote
This highlights the critical nature of managing caloric intake in at-risk patients.
176
How can hypophosphatemia be prevented in patients at risk for RFS?
Feeding should consist of low calories with gradual increase to maintain the target caloric intake.
## Footnote
This approach helps to mitigate the risk of electrolyte imbalances.
177
What other electrolyte abnormalities can occur along with hypophosphatemia due to high glucose?
* Hypokalemia
* Hypomagnesemia.
## Footnote
These conditions further complicate the management of patients experiencing RFS.
178
What supplementation can help prevent RFS?
Supplementation of K⁺, Mg²⁺, and phosphate along with nutrition.
## Footnote
This strategy helps to correct electrolyte imbalances and supports patient recovery.
179
What percentage of kidney transplantation patients develop mild to moderate hypophosphatemia?
About 90%.
## Footnote
This condition may last for months to years post-transplant.
180
What are some causes of hypophosphatemia following kidney transplantation?
* Tertiary hyperparathyroidism
* Elevated FGF-23 levels
* Vitamin D deficiency.
## Footnote
These factors contribute to phosphate wasting in transplanted patients.
181
What treatment improves both PTH levels and phosphate wasting in kidney transplant patients?
Cinacalcet.
## Footnote
This medication is used to manage hyperparathyroidism and its effects on phosphate metabolism.
182
What electrolyte disorder is frequently observed in critically ill patients?
Hypophosphatemia.
## Footnote
It is a common electrolyte disorder during ICU stays.
183
What are common causes of hypophosphatemia in critical care units?
* Glucose-containing solutions
* Insulin administration
* Starvation
* Refeeding
* Sepsis
* Shock
* Trauma
* Postoperative state
* Respiratory alkalosis
* Metabolic acidosis
* Medications such as catecholamines and diuretics
* Kidney replacement therapies.
## Footnote
These causes highlight the multifactorial nature of electrolyte disturbances in critically ill patients.
184
What is the first step in diagnosing hypophosphatemia?
Establish the cause from history, physical examination, and clinical setting.
185
What should be inquired about during the history taking for hypophosphatemia?
Signs and symptoms, history of alcoholism, medications, dietary intake, IV fluids, and diagnosis.
186
Which system should be focused on during the physical examination for hypophosphatemia?
Musculoskeletal system.
187
What are signs of rhabdomyolysis in hypophosphatemia?
Muscle tenderness and pain.
188
What indicates rickets in children during physical examination?
Pathologic or pseudofractures and skeletal deformities.
189
What features indicate chronic hypophosphatemia in adults?
Rachitic features.
190
What is indicated by short stature with increased upper to lower body ratio?
Previous childhood rickets.
191
What condition is associated with sinus tumors in the context of hypophosphatemia?
Tumor-induced osteomalacia (TIO).
192
What might hepatomegaly suggest in a patient with hypophosphatemia?
Chronic alcoholism or tumors.
193
What physical examination finding suggests X-linked hypophosphatemia in adults?
Limited spine, joint, and hip motion.
194
What serum electrolytes should be measured in the evaluation of hypophosphatemia?
Ca²⁺, phosphate, Mg²⁺, alkaline phosphatase, and GFR.
195
What urine tests are relevant in diagnosing hypophosphatemia?
Urine phosphate, phosphate, creatinine, and pH.
196
What does a fractional excretion of phosphate (FEₚₒ₄) <5% suggest?
Nonkidney loss of phosphate.
197
What does a fractional excretion of phosphate (FEₚₒ₄) >5% suggest?
Kidney origin of hypophosphatemia.
198
What is the formula for calculating tubular reabsorption of phosphate (TRP)?
TRP = 1 - FEₚₒ₄.
199
What is the normal range for TmP/GFR in adults?
0.8–1.35 mmol/L.
200
What does TmP/GFR <0.8 indicate?
Kidney phosphate wasting.
201
Which serum and urine levels are helpful in diagnosing various causes of hypophosphatemia?
Ca²⁺, PTH, 25(OH)D₃, 1,25(OH)₂D₃, and FGF-23.
202
What do increased alkaline phosphatase and PTH levels suggest?
Primary or secondary hyperparathyroidism and FGF-23-mediated hypophosphatemia.
203
In which conditions are serum FGF-23 levels elevated?
X-linked hypophosphatemia, ADHR, ARHR, TIO, and after kidney transplantation.
204
What imaging studies are useful for chronic hypophosphatemia?
* Plain radiographs for fractures and skeletal abnormalities
* Dual-energy x-ray absorptiometry scan for bone density and osteomalacia
* Bone scan for increased uptake of technetium in osteomalacia
* CT, MRI, PET for TIO.
205
What is the primary goal in the treatment of hypophosphatemia?
Removing the causes such as medications or dietary deficiency whenever possible.
206
What is considered severe hypophosphatemia in mg/dL?
<1.0 mg/dL
207
What is the treatment for acute severe symptomatic hypophosphatemia?
IV administration of either sodium or potassium phosphate with frequent monitoring of serum [Pi].
208
What is the infusion rate for phosphorus in hyperalimentation-induced hypophosphatemic patients?
Not exceeding 7.5 mmol/h.
209
What percentage of severe hypophosphatemic patients benefited from tailored IV phosphorus regimens according to Taylor et al.?
63%
210
What percentage of moderately hypophosphatemic patients benefited from tailored IV phosphorus regimens according to Taylor et al.?
78%
211
Fill in the blank: In surgical intensive care patients, sodium or potassium phosphate is dissolved in 250 mL of ______ and infused over 6 hours.
D5W
212
What are the two types of phosphate preparations listed in Table 21.4?
Intravenous and Oral
213
What is the phosphate content of Neutral Na/K PO₄ preparation?
1.1 mmol/mL
214
What is the phosphate content of Neutra-phos oral preparation?
250 mg/packet
215
What is the phosphate repletion protocol for a serum phosphate level of <0.32 mmol/L for a patient weighing 61-80 kg?
40 mmol
216
True or False: IV phosphate administration is associated with hypocalcemia and hyperphosphatemia.
True
217
What is suggested to suppress PTH levels during oral therapy for chronic hypophosphatemia?
Concomitant administration of calcitriol.
218
What may improve hypophosphatemia in kidney transplant patients?
An increase in dietary phosphate.
219
What is the primary treatment for chronic hypophosphatemia?
Oral therapy.
220
Fill in the blank: Long-term oral therapy may suppress 1,25(OH)₂D₃ levels and raise ______ and FGF-23 levels.
PTH
221
What is the phosphate content of K-phos original preparation?
150 mg/capsule
222
What is the phosphate content of potassium PO₄ preparation?
3 mmol/mL
