17-hydroxyprogesterone (17-OHP) is a steroid hormone precursor, primarily produced in the adrenal glands, small organs above the kidneys. It is also produced to a lesser extent in the gonads (ovaries and testes) and the placenta during pregnancy. Measuring 17-OHP levels can provide insights into the body’s hormone balance and may indicate certain underlying health conditions.
Understanding 17 Hydroxyprogesterone
17-OHP is a precursor in the adrenal glands’ process of making cortisol, a hormone that regulates stress response, metabolism, and immune function. The conversion of 17-OHP to cortisol involves specific enzymes, notably 21-alpha hydroxylase and 11-beta hydroxylase. If there is a deficiency in these enzymes, the normal metabolic pathway is disrupted, leading to an accumulation of 17-OHP in the body.
Beyond its role in cortisol production, 17-OHP can also be converted into androgens, which are male sex hormones like testosterone. This conversion is facilitated by enzymes such as 17,20 lyase. 17-OHP functions as a building block for both cortisol and androgens.
Reasons for Testing 17 Hydroxyprogesterone Levels
A healthcare provider may order a 17-OHP test when an imbalance in adrenal hormone production is suspected. One common reason is newborn screening for congenital adrenal hyperplasia (CAH), an inherited disorder where the adrenal glands cannot produce enough cortisol. In the United States, this is routinely done as a heel-stick blood test for all newborns to detect the most common type of CAH, which is 21-hydroxylase deficiency.
The test is also used to evaluate infants with ambiguous genitalia, where the external sex organs are not clearly male or female, as this can be a symptom of CAH. In older children and adults, 17-OHP testing may be performed to investigate symptoms of adrenal insufficiency or excess. These symptoms can include lethargy, poor feeding, dehydration, low blood pressure, or, in females, excess facial and body hair (hirsutism), irregular menstrual periods, acne, and infertility.
For male children, premature sexual development, such as early puberty, might also prompt this test. The 17-OHP test is typically a blood test, where a sample is collected from a vein in the arm, or from a heel stick for infants. It can also be used to monitor the effectiveness of treatment in individuals already diagnosed with CAH.
Interpreting Your 17 Hydroxyprogesterone Results
Interpreting 17-OHP results involves understanding what normal, high, or low levels might indicate. Normal 17-OHP levels generally suggest that congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency is unlikely. For adults, a normal level is typically less than 200 ng/dL (6.06 nmol/L), while in children before puberty, it’s around 100 ng/dL (3.03 nmol/L).
High Levels
Elevated 17-OHP levels often point to congenital adrenal hyperplasia (CAH), especially the most common form caused by a deficiency in the 21-hydroxylase enzyme. Without enough 21-hydroxylase, the adrenal glands struggle to produce cortisol, leading to an accumulation of 17-OHP and an overproduction of male sex hormones (androgens). Infants with classical (severe) CAH typically show 17-OHP levels ranging from 2,000 to 40,000 ng/dL (60.6 to 1212 nmol/L), while adults with non-classical (milder) CAH may have levels above 200 ng/dL (6.06 nmol/L), sometimes reaching over 1,500 ng/dL after ACTH stimulation.
CAH presents in different forms. Classical CAH is severe and often diagnosed at birth, sometimes with ambiguous genitalia in female infants or salt-wasting crises in both sexes. Non-classical CAH is milder and may appear later in childhood or adulthood with symptoms like premature puberty, acne, hirsutism, or irregular periods. To confirm a CAH diagnosis, especially in cases with moderately elevated baseline 17-OHP, an ACTH (adrenocorticotropic hormone) stimulation test may be performed. This test involves measuring 17-OHP levels before and after an injection of synthetic ACTH; a significant increase in 17-OHP (typically above 30 nmol/L or 1,104 ng/dL at 60 minutes post-stimulation) is indicative of CAH.
Other less common causes of elevated 17-OHP can include adrenal tumors or polycystic ovary syndrome (PCOS). In PCOS, 17-OHP values can be significantly elevated due to ovarian production, although the ACTH stimulation test helps differentiate it from non-classical CAH.
Low Levels
Lower than normal 17-OHP levels can indicate that the adrenal glands are not producing sufficient amounts of this precursor hormone. This may impact the subsequent production of cortisol and sex hormones. Conditions such as primary adrenal insufficiency (Addison’s disease) or issues that impair ACTH production can lead to low 17-OHP levels. Symptoms associated with low 17-OHP may include fatigue, muscle weakness, low blood pressure, weight loss, mood swings, and irregular menstrual cycles.
Managing Abnormal 17 Hydroxyprogesterone Levels
Managing abnormal 17-OHP levels depends on the underlying diagnosis. For individuals diagnosed with congenital adrenal hyperplasia (CAH), the primary approach involves hormone replacement therapy. Glucocorticoids, such as hydrocortisone, are commonly used to replace the deficient cortisol and suppress the excess production of androgens from the adrenal glands.
The aim of this treatment is to normalize hormone levels, reduce symptoms like virilization or early puberty, and prevent complications such as adrenal crisis. Dosing of glucocorticoids is carefully adjusted based on the patient’s age and the severity of the condition, with regular monitoring of 17-OHP levels, electrolytes, blood pressure, and growth. In cases of salt-wasting CAH, mineralocorticoid replacement, such as fludrocortisone, and salt supplementation may also be necessary.
For other conditions that might cause elevated 17-OHP, such as polycystic ovary syndrome (PCOS), management focuses on addressing the specific symptoms. This can include hormonal contraceptives to regulate menstrual cycles, fertility medications if conception is desired, and lifestyle modifications like diet and exercise to manage symptoms. If an adrenal tumor is the cause, surgical removal might be considered. Ongoing monitoring by an endocrinologist is recommended to adjust treatment as needed.