Principles of Maternal Hormone Examination and Laboratory Diagnostics and Clinical Significance

Principles of Maternal Hormone Examination

FSH (Follicle Stimulating Hormone) and LH (Luteining Hormone) are glycoproteins produced in the anterior pituitary gland. Their production is regulated in response to stimulation by Gonadotropin Releasing Hormone (GNRH), which was formerly known as luteinizing-releasing hormone. GNRH is stimulated when the circulating levels of estrogen in women or testosterone in men are low. This operates through a feedback mechanism where the hypothalamus is stimulated to release GNRH, which then stimulates the production and release of LH and FSH. These hormones subsequently act on the gonads (ovaries or testes). In females, FSH stimulates the development of follicles in the ovary, while in males, it stimulates the development of Sertoli cells.

LH plays several critical roles in female reproduction, including the stimulation of estrogen production, the induction of ovulation, and the formation of the corpus luteum within the follicle. In males, LH stimulates the Leydig cells to produce testosterone. Once sufficient levels of estrogen or testosterone are produced, FSH and LH production is inhibited through feedback. FSH is essential for the maturation of both ovaries and testes and is required along with LH for sperm production. In women, these hormones are secreted at varying levels throughout the menstrual cycle. A mid-cycle peak of FSH is necessary for follicle and ovum formation, and LH must also peak concurrently to trigger ovulation or the formation of a luteal corpus that can support an embryo if fertilization occurs.

Normal Reference Values for FSH and LH

Reference values for LH and FSH may vary depending on the specific assay method used. For adults, the normal findings are as follows. Adult males typically exhibit LH levels between $1.24-7.8\,IU/L$ and FSH levels between $1.42-15.4\,IU/L$. Adult females have varying levels based on their cycle phase: during the follicular phase, LH is $1.68-15\,IU/L$ and FSH is $1.37-9.9\,IU/L$; at the ovulatory peak, LH reaches $21.9-56.6\,IU/L$ and FSH reaches $6.17-17.2\,IU/L$; during the luteal phase, LH is $0.61-16.3\,IU/L$ and FSH is $1.09-9.2\,IU/L$. Postmenopausal women show significantly higher levels, with LH at $14.2-52.3\,IU/L$ and FSH ranging from $19.3-100.6\,IU/L$. Children aged $1-10\,years$ show lower ranges: males have LH at $0.04-3.6\,IU/L$ and FSH at $0.3-4.6\,IU/L$, while females have LH at $0.03-3.9\,IU/L$ and FSH at $0.68-6.7\,IU/L$.

Clinical Significance and Interfering Factors for FSH/LH

Increased levels of FSH and LH can indicate gonad failure, which occurs in conditions such as menopause, Turner syndrome, Klinefelter syndrome, castration, anorchia, hypogonadism, Polycystic Ovary Syndrome (PCO), and feminization syndrome. In these cases, low estrogen or testosterone levels cause a maximum increase in FSH and LH through feedback mechanisms. Precocious puberty is another cause for over-secretion. Conversely, decreased levels may indicate pituitary failure, as FSH and LH are produced in the anterior pituitary; a reduction in these hormones is often the first indicator of pituitary issues. Hypothalamic failure also causes low levels because GNRH is not produced to stimulate FSH/LH. Other causes for decreased levels include stress, anorexia nervosa, and malnutrition, though the exact pathophysiology for these is not fully clear. Pituitary adenomas may sometimes secrete FSH and LH independently of feedback mechanisms.

Several factors can interfere with FSH/LH testing. Human chorionic gonadotropin (hCG) and thyroid-stimulating hormone (TSH) can cause falsely high LH levels in some immunoassay methods due to molecular similarities, particularly in patients with hCG-producing tumors or hypothyroidism. Drugs that may increase levels include anticonvulsants, cimetidine, clomiphene, digitalis, levodopa, naloxone, and spironolactone. Drugs that may decrease levels include digoxin, estrogens, oral contraceptives, progesterones, steroids, testosterone, and phenothiazines. For the procedure, fasting is not required, and a red-top blood tube is commonly used. The laboratory request should indicate the date of the last menstrual period or if the woman is postmenopausal.

Progesterone Function and Monitoring

Progesterone acts primarily on the endometrium, initiating the secretory phase to prepare for the implantation of a fertilized ovum. It is typically secreted by the corpus luteum following ovulation. During the first few weeks of pregnancy, the corpus luteum continues this production until the placenta takes over. Serum progesterone and its urinary metabolite, pregnanediol, increase significantly during the latter half of a normal ovulatory cycle. Monitoring progesterone levels provides information regarding the occurrence and timing of ovulation, which is particularly useful for women who have difficulty conceiving. Plasma levels rise after ovulation alongside LH, peaking for approximately $6$ to $10\,days$ before falling to trigger menstruation. Blood samples taken on day $8$ and day $21$ of the cycle that show a high increase in the latter specimen indicate successful ovulation.

In pregnancy, progesterone levels rise due to placental production. Repeated testing can monitor placental status in high-risk pregnancies or evaluate those with an inadequate luteal phase requiring progesterone supplementation to maintain early pregnancy. For testing, fasting is not required, and serum is collected in a red-top tube. Normal reference values for adult males are $10-50\,ng/mL$. For adult females, levels are $<50\,ng/mL$ in the follicular phase, $300-2500\,ng/mL$ in the luteal phase, and $<40\,ng/mL$ post-menopause. Trimester-specific ranges for pregnancy are: Trimester 1 ($725-4400\,ng/mL$), Trimester 2 ($1950-8250\,ng/mL$), and Trimester 3 ($6500-22900\,ng/mL$).

Clinical Implications of Progesterone Levels

Increased progesterone levels are seen in normal ovulation (due to the corpus luteum), healthy pregnancies (where the placenta maintains the pregnancy), and ovarian luteal cysts, which can produce progesterone for extended periods. Molar pregnancies (hydatidiform mole) also produce progesterone, though levels may be lower than in normal pregnancies. Decreased levels are associated with preeclampsia, toxemia of pregnancy, threatened abortion, and placental failure. Fetal death leads to decreased placental viability and lower progesterone. Ovarian cancer can damage ovarian tissue function, leading to reduced levels. Conditions like amenorrhea and ovarian hypofunction result in lower levels because the corpus luteum does not form without ovulation.

Estrogen: Types and Clinical Significance

Estrogen measurements are used to evaluate sexual maturity, menstrual problems, and fertility issues. There are three main types of estrogen. E1 (Estrone) is secreted by the ovaries but mostly converted from androstenedione in peripheral tissues; it is the primary circulating estrogen after menopause. E2 (Estradiol) is mostly produced in the ovaries and is the most frequently measured form to evaluate fertility, menstrual issues, sexual maturity, and various syndromes like gynecomastia. Low E2 levels stimulate the hypothalamus to produce GNRH. E3 (Estriol) is the major estrogen during pregnancy, produced by the placenta from precursors made by the fetal liver and adrenal glands. Monitoring E3 is a critical index of feto-placental well-being. Rising levels indicate normal growth, while falling levels may indicate fetal distress, preeclampsia, diabetes complications, or fetal death, necessitating immediate assessment or potentially indicating premature labor.

Normal Estradiol (E2) serum levels for adult females range from $20-350\,pg/mL$ in the follicular phase, $150-750\,pg/mL$ at the mid-cycle peak, and $30-450\,pg/mL$ in the luteal phase. Urine Estriol (E3) in pregnant women increases from Trimester 1 ($0-800\,mcg/24\,hr$) to Trimester 3 ($5000-12000\,mcg/24\,hr$). Increased estrogen levels occur in feminization syndromes, precocious puberty (often due to adrenal cortisol metabolism defects), ovarian/testicular/adrenal tumors, and normal or multiple pregnancies. Liver cirrhosis or necrosis can also increase levels because the liver is responsible for catabolizing estrogens. Hyperthyroidism increases thyroid-binding globulin, which elevates serum total T4 linked to estrogens. Decreased levels are seen in failing pregnancies, Turner syndrome (missing X chromosome), hypopituitarism, hypogonadism, Stein-Leventhal syndrome, menopause, and anorexia nervosa (due to reduced sterol precursors for synthesis).

Human Chorionic Gonadotropin (hCG) Characteristics

Pregnancy tests are based on detecting hCG, which is secreted by the placental trophoblast after fertilization. It appears in blood and urine within days of conception. In early weeks, levels rise sharply, with serum levels initially higher than urine levels; after one month, the concentrations are similar in both. hCG consists of an alpha subunit (shared with TSH, FSH, and LH) and a specific beta subunit. Most laboratory methods use a sandwich-type immunoassay. In this technique, monoclonal antibodies directed against the alpha and beta subunits are applied to a solid-phase substrate. A labeled monoclonal antibody directed at the beta subunit binds to create the "sandwich," and the amount of labeled subunit identifies the hCG concentration.

Modern sandwich immunoassays can detect pregnancy $3$ to $7\,days$ after conception due to high sensitivity and the elimination of cross-reactions with other glycoproteins. The diagnostic threshold for pregnancy is $>25\,IU/L$. Values between $5$ and $25\,IU/L$ are inconclusive and require re-testing within $72\,hours$. During the first $6\,weeks$, hCG levels should double every $3\,days$. When hCG levels reach between $1000$ and $2000\,IU/L$, the embryo should be visible via transvaginal ultrasound. If hCG is high but no gestational sac is visible in the uterus, an ectopic pregnancy is suspected. Very high levels ($>30000\,mIU/mL$) are typical for healthy pregnancy, while lower levels in the presence of positive results may indicate ectopic pregnancy, threatened abortion, or incomplete abortion. High levels are also associated with molar pregnancies, choriocarcinomas, and germ cell tumors of the testes or ovaries.

Laboratory Procedures and Methodology (EIA and Immunochromatography)

Enzyme Immunoassay (EIA) uses enzymes (such as Horseradish peroxidase, Alkaline phosphatase, Glucose-6-phosphate dehydrogenase, or B-D-galactosidase) as labels. When a substrate is added, it produces a color change measured via colorimetry. In competitive EIA, labeled and unlabeled antigens compete for limited antibody binding sites; enzyme activity is inversely proportional to the antigen concentration. Non-competitive EIA (often called indirect ELISA) has higher sensitivity (down to $<1\,pg/mL$). In this method, the patient's antibody is incubated with a solid-phase antigen, followed by an enzyme-labeled anti-immunoglobulin. The resulting color development is directly proportional to the amount of patient antibody present.

Rapid testing often uses immunochromatography (using antibodies and colloidal gold), which is fast, requires no electricity, and allows reagents to be stored at room temperature (max $25^{\circ}C$). However, it has limitations: visual reading is subjective, timing must be precise, adequate lighting is necessary, and it provides no permanent record. To overcome subjectivity, results should be read by three people separately. False-negative hCG results can occur if the test is performed too early or if the urine is dilute (often due to diuretics or promethazine). False-positives can be caused by hematuria, proteinuria, or drugs like anticonvulsants, antiparkinsonians, hypnotics, and tranquilizers (especially promazine). For serum testing, a red-top tube is used, and hemolysis must be avoided as it interferes with results.