21-Hydroxyprogesterone

21-Hydroxyprogesterone is a vital biomarker in the realm of en21-hydroxyprogesteronerine diagnostics, serving as a key indicator of adrenal function and steroid metabolism. This steroid hormone plays a critical role in the biosynthesis of glucocorticoids and mineralocorticoids, essential components in managing stress responses, blood pressure, and electrolyte balance. The measurement of 21-Hydroxyprogesterone is particularly important in diagnosing and managing conditions such as Congenital Adrenal Hyperplasia (CAH), where the enzyme responsible for its conversion is deficient.

Overview of 21-Hydroxyprogesterone

Biological Role and Clinical Significance  [2., 4., 14.]  

21-Hydroxyprogesterone, also called 21-hydroxyprogesterone and 11-desoxycorticosterone, is a precursor in the synthesis of glucocorticoids and mineralocorticoids.  [4., 14.]

Glucocorticoid and mineralocorticoid hormones are essential for regulating metabolism, immune response, and salt-water balance. 

21-hydroxyprogesterone is produced primarily in the adrenal cortex.  As a glucocorticoid and mineralocorticoid precursor, it is instrumental in the body's response to stress and helps manage carbohydrate metabolism, inflammation, and blood pressure. 

The proper functioning of 21-Hydroxyprogesterone synthesis is essential for overall health, and its levels can provide valuable insights into adrenal gland function and the body’s ability to produce vital hormones.

In healthy individuals, 21-hydroxyprogesterone exhibits relatively weak mineralocorticoid activity, approximately 1/20th that of aldosterone.  

However, in certain forms of congenital adrenal hyperplasia (CAH), such as those involving 11β-hydroxylase or 17α-hydroxylase deficiencies, 21-hydroxyprogesterone levels can rise significantly.  This accumulation can lead to mineralocorticoid hypertension, characterized by low renin and aldosterone levels. 

Consequently, measuring 21-hydroxyprogesterone levels is valuable for diagnosing and managing these specific forms of CAH. 

Additionally, 21-hydroxyprogesterone can be abnormally produced by adrenal tumors, leading to similar hypertension symptoms. 

21-hydroxyprogesterone levels are also monitored in patients on drugs that inhibit 11β-hydroxylase, such as metyrapone for Cushing's syndrome or azole antifungals like posaconazole, as these medications can increase 21-hydroxyprogesterone concentrations and lead to mineralocorticoid hypertension.  [2.] 

21-Hydroxyprogesterone Production

The biochemical pathway for the production of 21-hydroxyprogesterone is as follows:

• Cholesterol is converted to pregnenolone, which is then converted to progesterone by 3β-hydroxysteroid dehydrogenase.  

• Progesterone is then hydroxylated at the C21 position by 21-hydroxylase (encoded by the CYP21A2 gene) to form 21-hydroxyprogesterone.  

21-hydroxyprogesterone can then undergo further modifications:

• 11β-hydroxylation by 11β-hydroxylase (encoded by the CYP11B1 gene) to form corticosterone

• Conversion to aldosterone via intermediate steps catalyzed by aldosterone synthase (encoded by the CYP11B2 gene) in the adrenal glomerulosa

21-hydroxyprogesterone is a precursor for aldosterone production, but it is not a major secretory hormone itself.  

21-Hydroxyprogesterone and Congenital Adrenal Hyperplasia (CAH)

Definition of Congenital Adrenal Hyperplasia  [12.]

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders characterized by various enzyme defects in the adrenal glands that disrupt steroid hormone synthesis, including glucocorticoids, mineralocorticoids, and sex steroids. 

These deficiencies arise from mutations in genes encoding these enzymes, primarily impacting the production of cortisol and, to a lesser extent, aldosterone. 

Because cortisol production is critical for regulating various bodily functions including metabolism and the immune response, its deficiency can lead to symptoms ranging from mild to life-threatening.

The lack of cortisol stimulates the pituitary gland to release more adrenocorticotropic hormone (ACTH), which in turn causes the adrenal glands to enlarge and produce excess androgens.

The most common form is due to a deficiency in 21-hydroxylase which affects 90%-95% of cases and leads to excessive androgen production and a spectrum of clinical presentations from ambiguous genitalia at birth to non-classic forms with later onset including early signs of puberty in children, and fertility issues in adults.

CAH can also result in severe salt-wasting forms which increase neonatal morbidity and mortality, making early diagnosis and treatment essential. 

Depending on the specific enzyme affected and the severity of the deficiency, CAH can be categorized as either classical (severe) or non-classical (mild). Treatment typically involves hormone replacement therapy to correct the deficiencies and manage symptoms.

Newborn Screening for Congenital Adrenal Hyperplasia

Newborn screening for 17-hydroxyprogesterone, which is used to detect congenital adrenal hyperplasia (CAH), is widely implemented but not universally conducted in every country. 

In the United States, it is included in the routine newborn screening panel as a heel stick in all states, helping to identify infants with CAH early so that treatment can begin promptly.  [9.]‌

Causes of Congenital Adrenal Hyperplasia

Congenital adrenal hyperplasia (CAH) is primarily caused by genetic defects in enzymes that are crucial for cortisol synthesis.  The different enzyme deficiencies that lead to various forms of CAH include:

21-Hydroxylase Deficiency  [7.]

An autosomal recessive condition, this is the most common cause of CAH, accounting for about 90-95% of all CAH cases. 

It affects the conversion of 17-hydroxyprogesterone to 11-deoxycortisol and progesterone to 21-hydroxyprogesterone, ultimately manifesting in impaired cortisol synthesis in the adrenal glands. This deficiency prompts the need for lifelong glucocorticoid and mineralocorticoid replacement therapy. 

Effective management of this condition relies heavily on an interprofessional healthcare team to optimize patient outcomes. 

Early diagnosis through newborn screening, which measures 17-hydroxyprogesterone levels, is crucial for preventing severe complications such as adrenal crisis and virilization. 

The management strategy includes regular monitoring and adjusting hormone therapy to mitigate symptoms and prevent long-term complications.

11β-Hydroxylase Deficiency  [5.]

The second most common cause, affecting the conversion of 11-deoxycortisol to cortisol and 21-hydroxyprogesterone to corticosterone.

CAH due to 11β-hydroxylase deficiency (11βOHD) is a rare, autosomal recessive form, constituting only 0.2-8% of all CAH cases.  

A case involving a three-year-old girl diagnosed with classical CAH illustrates this condition's complexity: despite receiving regular hydrocortisone treatment, she presented with atypical genitalia and persistent hypertension. Genetic analysis revealed a novel homozygous mutation (c.53dup p.(Gln19Alafs*21)) in the CYP11B1 gene, confirming 11βOHD. 

This case underscores the importance of considering 11βOHD in CAH patients with persistent hypertension, as typical biomarkers might not always align with this diagnosis.

3β-Hydroxysteroid Dehydrogenase Deficiency  [1.]

3-beta-hydroxysteroid dehydrogenase (3ß-HSD) deficiency is an autosomal recessive congenital adrenal hyperplasia (CAH) that impacts the conversion of pregnenolone to progesterone and 17-hydroxypregnenolone to 17-hydroxyprogesterone, leading to reduced production of cortisol, aldosterone, and sex steroids. 

This deficiency manifests differently across genders; affected males often experience pseudohermaphroditism due to impaired androgen synthesis, showing incomplete masculinization of the external genitalia, while females may show normal differentiation or mild virilization. 

The disorder is categorized into three types: salt-wasting, non-salt-wasting, and non-classic. 

The salt-wasting type, the most severe, involves significant sodium loss, posing immediate life-threatening risks like dehydration and poor feeding. The non-salt-wasting type maintains enough hormone production for sodium reabsorption, and the non-classic type exhibits the mildest symptoms without salt wasting. 

Both males and females with this condition may face fertility challenges, and females can also experience irregular menstruation and excessive body hair from childhood or puberty. 

Prompt diagnosis and treatment are critical, especially for newborns with the salt-wasting form to prevent fatal outcomes.

17α-Hydroxylase/17,20-Lyase Deficiency  [15.]

17α-hydroxylase/17,20-lyase deficiency, a rare autosomal recessive form of congenital adrenal hyperplasia (CAH), is caused by mutations in the CYP17A1 gene. 

This deficiency leads to significantly reduced production of cortisol, estrogens, and androgens, resulting in an accumulation of mineralocorticoid precursors that cause symptoms like hypertension and hypokalemia. 

Patients may also experience sexual development issues including primary amenorrhea and sexual infantilism in genetically female individuals and ambiguous genitalia in genetically male individuals. Treatment typically involves glucocorticoid and sex steroid replacement to manage hormone levels and alleviate symptoms. 

The disorder is characterized by over 90 identified genetic mutations, varying in prevalence across different ethnic groups. A case highlighted in the study involves a 17-year-old female presenting with primary amenorrhea and lack of secondary sexual characteristics, who was treated with prednisolone and ethinyl estradiol.

P450 Oxidoreductase Deficiency  [10.] 

Cytochrome P450 oxidoreductase deficiency (PORD) is an autosomal recessive disorder that affects steroidogenesis, presenting a broad range of symptoms from cortisol deficiency and skeletal abnormalities to disorders of sex development (DSD).  

Patients may exhibit cortisol production but cannot adequately increase cortisol levels during stress, and might experience mild mineralocorticoid excess leading to hypertension in adulthood. 

PORD can cause ambiguous genitalia in both sexes, ovarian cysts in females, under-masculinization in males, and maternal virilization during pregnancy if the fetus is affected.

PORD shows impaired activity of enzymes like 17α-hydroxylase and 21-hydroxylase essential for cortisol, aldosterone, and sex steroid synthesis. Confirmatory molecular genetic testing identifies pathogenic variants in the POR gene.

Management includes glucocorticoid replacement for cortisol deficiency, surgical interventions for skeletal and genital abnormalities, and hormone therapies for sex steroid deficiencies. Monitoring and early intervention aim to manage developmental delays and prevent complications such as adrenal crisis.

Congenital Lipoid Adrenal Hyperplasia (StAR Deficiency)  [11.]

Lipoid congenital adrenal hyperplasia (lipoid CAH), the most severe form of CAH, is typically caused by mutations in the steroidogenic acute regulatory protein (STAR). These mutations disrupt the transfer of cholesterol within mitochondria, essential for synthesizing pregnenolone, the precursor of all steroid hormones.

 A study involving a Scandinavian infant with a salt-losing crisis revealed two de novo heterozygous mutations in the STAR gene, highlighting that lipoid CAH can arise from spontaneous mutations and is not limited to specific geographic regions.

This form of CAH is characterized by severe adrenal insufficiency from birth, often manifesting as a salt-losing crisis due to the inability to synthesize adequate mineralocorticoids and glucocorticoids.

Management of lipoid CAH requires prompt and aggressive treatment with glucocorticoid replacement to address cortisol deficiency and manage the salt-losing crisis. 

This case underscores the importance of considering lipoid CAH in the differential diagnosis of adrenal insufficiency in newborns, even in the absence of a family history, due to the possibility of de novo mutations.

Lab Testing for 21-Hydroxyprogesterone  

Testing for 21-Hydroxyprogesterone Levels, Sample Collection and Preparation

21-hydroxyprogesterone may be tested via blood or urine.  

Blood samples are typically collected from the patient via venipuncture, with serum or plasma separated from whole blood by centrifugation. 

Urine collection may be done from home, often over 24 hours.    

Patients may be instructed to fast or avoid certain medications prior to sample collection to prevent potential interference with hormone levels.

Interpretation of Test Results

Optimal Levels for 21-Hydroxyprogesterone

It is essential to consult the laboratory company used for their recommendations on lab interpretation.  One company reports the reference range for 21-hydroxyprogesterone in urine over 24 hours as:  [13.]

0.3-1.4 ng/mg creatinine/24 hours

The levels of 21-hydroxyprogesterone in blood tests vary widely depending on an individual’s age, gender, and for cycling women, the timing of their menstrual cycle.  Levels are also expected to change in pregnancy.  

An example of reference ranges in blood includes: [3.]

Male: 3.5-11.5 ng/dL

Female:

• Follicular phase: 1.5-8.5 ng/dL

• Luteal phase: 3.5-13 ng/dL

• Pregnancysome text
  • 1st trimester: 5-25 ng/dL

• 2nd trimester: 10-75 ng/dL

• 3rd trimester: 30-110 ng/dL

Children:

• < 1 y: 7-57 ng/dL

• 1-5 y: 4-49 ng/dL

• 6-12 y: some text
  • Male: 9-34 ng/dL

• Female: 2-13 ng/dL

Elevated Levels of 21-Hydroxyprogesterone  [2., 3.]

Elevated levels of 21-hydroxyprogesterone can have significant clinical implications.  

The most common cause is 11β-hydroxylase deficiency, a form of congenital adrenal hyperplasia (CAH).  This enzymatic defect leads to decreased production of cortisol and accumulation of 21-hydroxyprogesterone and other steroid precursors.

Clinically, 11β-hydroxylase deficiency can manifest as hypertension, often in early childhood, and hyperandrogenism, which may cause ambiguous genitalia in female newborns and precocious puberty in both genders.

Elevated 21-hydroxyprogesterone levels are also seen in other conditions affecting adrenal steroidogenesis, such as adrenocortical carcinoma.

However, an isolated elevation of 21-hydroxyprogesterone is not diagnostic for any specific disease, and it should be measured along with other hormones like 11-deoxycortisol, 17-hydroxyprogesterone, aldosterone, and cortisol to establish the underlying cause

Low Levels of 21-Hydroxyprogesterone

Low levels of 21-hydroxyprogesterone are not considered clinically significant.  

Related Biomarkers and Co-Testing

While 21-Hydroxyprogesterone is a critical biomarker for diagnosing certain adrenal disorders, assessing it alongside other related hormones and biomarkers can provide a more comprehensive understanding of hormone balance.

Cortisol and ACTH

Cortisol and Adrenocorticotropic Hormone (ACTH) are essential biomarkers that are often measured alongside 21-Hydroxyprogesterone. 

Cortisol, another steroid hormone produced by the adrenal glands, plays a key role in metabolism and stress response. Measuring cortisol levels can help assess whether the adrenal glands are producing appropriate amounts of steroid hormones. 

ACTH stimulates the production of cortisol, so its levels can indicate whether the pituitary gland is functioning properly in its role of regulating adrenal output. 

Testing for these hormones together with 21-Hydroxyprogesterone can help pinpoint the nature of adrenal hormone abnormalities.

Additional Hormonal Assessments

In addition to cortisol and ACTH, testing for other adrenal and gonadal hormones such as 17-Hydroxyprogesterone and androstenedione can be informative.

These hormones are part of the same biosynthesis pathway as 21-Hydroxyprogesterone and provide additional insights into the body's hormone production processes.  For example, 17-Hydroxyprogesterone is a precursor to 21-Hydroxyprogesterone and is also elevated in most cases of CAH.  Its assessment can help confirm a diagnosis and monitor treatment effectiveness. 

Androstenedione, a direct precursor to testosterone and estrogens, can help evaluate androgen levels and assess gonadal function.  [6.] 

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