Skip to main content

Chemistry

Result Interpretation

Interpreting endocrine test results requires careful consideration of various factors, including the patient’s clinical presentation, reference intervals, and potential interfering substances

General Principles of Test Result Interpretation

  • Reference Intervals
    • Use appropriate reference intervals for the specific assay and patient population
    • Reference intervals can vary based on age, sex, ethnicity, and geographic location
  • Clinical Context
    • Interpret test results in the context of the patient’s clinical history, physical examination findings, and other laboratory data
    • Consider the patient’s symptoms, medications, and any coexisting medical conditions
  • Multiple Tests
    • Often, a single hormone measurement is insufficient for diagnosis; multiple tests or dynamic tests may be necessary
    • Assess the pattern of hormone levels rather than relying on a single value
  • Interfering Substances
    • Be aware of potential interfering substances that can affect hormone measurements (e.g., heterophile antibodies, biotin, medications)
    • Consider repeating the test using a different method if interference is suspected
  • Assay Limitations
    • Understand the limitations of the specific assay used, including its sensitivity, specificity, and potential for cross-reactivity
    • Consult with the laboratory or manufacturer for guidance on test interpretation

Pituitary Hormone Interpretation

Growth Hormone (GH)

  • Normal
    • Basal GH: < 5 ng/mL (may vary by assay)
    • Suppression after glucose load: < 1 ng/mL
  • Elevated GH
    • Acromegaly (adults): Enlargement of hands, feet, and facial features; joint pain; excessive sweating; glucose intolerance
    • Gigantism (children): Excessive growth and height
    • Pituitary adenoma: Confirmed by imaging studies (MRI)
  • Suppressed GH
    • Growth hormone deficiency (GHD): Short stature in children, fatigue, decreased muscle mass, and increased body fat in adults
    • Hypopituitarism: May be associated with deficiencies of other pituitary hormones
    • Evaluate with stimulation testing (e.g., insulin tolerance test)

Adrenocorticotropic Hormone (ACTH)

  • Normal
    • Morning ACTH: 10-50 pg/mL (may vary by assay)
  • Elevated ACTH
    • Cushing’s disease: Pituitary adenoma causing excessive ACTH production
    • Ectopic ACTH syndrome: ACTH-secreting tumor outside the pituitary (e.g., small cell lung cancer)
    • Primary adrenal insufficiency: Lack of negative feedback from cortisol
  • Suppressed ACTH
    • Secondary adrenal insufficiency: Pituitary or hypothalamic dysfunction
    • Exogenous glucocorticoid use: Suppression of the hypothalamic-pituitary-adrenal (HPA) axis
    • Differentiate causes with stimulation and suppression testing (e.g., dexamethasone suppression test)

Thyroid-Stimulating Hormone (TSH)

  • Normal
    • TSH: 0.4-4.0 μIU/mL (may vary by assay)
  • Elevated TSH
    • Primary hypothyroidism: Thyroid gland failure
    • Hashimoto’s thyroiditis: Autoimmune destruction of the thyroid gland
    • Symptoms: Fatigue, weight gain, cold intolerance, constipation
  • Suppressed TSH
    • Hyperthyroidism: Excessive thyroid hormone production
    • Graves’ disease: Autoimmune stimulation of the thyroid gland
    • Toxic nodular goiter: Overactive thyroid nodules
    • Symptoms: Weight loss, anxiety, heat intolerance, palpitations
    • Central hypothyroidism: Pituitary or hypothalamic dysfunction
    • Evaluate with free T4 and T3 measurements

Prolactin

  • Normal
    • Prolactin: < 20 ng/mL (may vary by assay)
  • Elevated Prolactin (Hyperprolactinemia)
    • Prolactinoma: Pituitary tumor secreting prolactin
    • Medications: Antipsychotics, antidepressants, and other drugs
    • Pregnancy: Physiological increase in prolactin
    • Hypothyroidism: Elevated TSH can stimulate prolactin secretion
    • Symptoms: Galactorrhea (milk production), amenorrhea (absence of menstruation), infertility, and sexual dysfunction
  • Suppressed Prolactin
    • Hypopituitarism: May be associated with deficiencies of other pituitary hormones
    • Rarely clinically significant

Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH)

  • Normal
    • Varies depending on sex and menstrual cycle phase in women
  • Elevated LH and FSH
    • Primary hypogonadism: Gonadal failure (e.g., Klinefelter syndrome in men, Turner syndrome in women)
    • Polycystic ovary syndrome (PCOS): Elevated LH/FSH ratio
  • Suppressed LH and FSH
    • Secondary hypogonadism: Pituitary or hypothalamic dysfunction
    • Anabolic steroid use: Suppression of the hypothalamic-pituitary-gonadal (HPG) axis
    • Symptoms: Infertility, sexual dysfunction, and decreased secondary sexual characteristics

Thyroid Hormone Interpretation

Free Thyroxine (Free T4)

  • Normal
    • Free T4: 0.8-1.8 ng/dL (may vary by assay)
  • Elevated Free T4
    • Hyperthyroidism: Excessive thyroid hormone production
    • Graves’ disease: Autoimmune stimulation of the thyroid gland
    • Toxic nodular goiter: Overactive thyroid nodules
  • Suppressed Free T4
    • Hypothyroidism: Thyroid gland failure
    • Hashimoto’s thyroiditis: Autoimmune destruction of the thyroid gland
    • Central hypothyroidism: Pituitary or hypothalamic dysfunction
    • Evaluate in conjunction with TSH

Free Triiodothyronine (Free T3)

  • Normal
    • Free T3: 2.3-4.2 pg/mL (may vary by assay)
  • Elevated Free T3
    • Hyperthyroidism: Excessive thyroid hormone production
    • T3 toxicosis: Selective elevation of T3
  • Suppressed Free T3
    • Hypothyroidism: Thyroid gland failure
    • Non-thyroidal illness: Decreased conversion of T4 to T3
    • Evaluate in conjunction with TSH and free T4

Thyroid Antibodies

  • Thyroid Peroxidase Antibody (TPO Ab)
    • Elevated in Hashimoto’s thyroiditis and Graves’ disease
  • Thyroglobulin Antibody (Tg Ab)
    • Elevated in Hashimoto’s thyroiditis and Graves’ disease
  • TSH Receptor Antibody (TRAb)
    • Elevated in Graves’ disease
    • Confirms the diagnosis of autoimmune thyroid disease

Adrenal Hormone Interpretation

Cortisol

  • Normal
    • Morning cortisol: 5-25 μg/dL (may vary by assay)
    • Evening cortisol: < 5 μg/dL
  • Elevated Cortisol
    • Cushing’s syndrome: Excessive cortisol production
    • Cushing’s disease: Pituitary adenoma causing excessive ACTH production
    • Ectopic ACTH syndrome: ACTH-secreting tumor outside the pituitary
    • Adrenal tumor: Cortisol-secreting tumor in the adrenal gland
    • Exogenous glucocorticoid use: Iatrogenic Cushing’s syndrome
    • Evaluate with dexamethasone suppression test and ACTH measurement
  • Suppressed Cortisol
    • Adrenal insufficiency: Insufficient cortisol production
    • Primary adrenal insufficiency: Addison’s disease (adrenal gland failure)
    • Secondary adrenal insufficiency: Pituitary or hypothalamic dysfunction
    • Evaluate with ACTH stimulation test

Aldosterone

  • Normal
    • Varies depending on sodium intake and posture
  • Elevated Aldosterone
    • Primary hyperaldosteronism: Aldosterone-secreting tumor in the adrenal gland (Conn’s syndrome)
    • Secondary hyperaldosteronism: Increased renin production due to kidney disease or heart failure
    • Hypertension, hypokalemia, and metabolic alkalosis
  • Suppressed Aldosterone
    • Adrenal insufficiency: Adrenal gland failure
    • Congenital adrenal hyperplasia: Genetic defect in cortisol synthesis leading to increased androgens and decreased aldosterone
    • Evaluate in conjunction with renin measurement

Catecholamines (Epinephrine, Norepinephrine, Dopamine)

  • Elevated Catecholamines
    • Pheochromocytoma: Tumor of the adrenal medulla that produces excessive catecholamines
    • Symptoms: Hypertension, palpitations, sweating, and headaches
    • Evaluate with urine metanephrines and catecholamines

Parathyroid Hormone (PTH) Interpretation

  • Normal
    • PTH: 10-65 pg/mL (may vary by assay)
  • Elevated PTH
    • Primary hyperparathyroidism: Parathyroid adenoma or hyperplasia causing excessive PTH production and hypercalcemia
    • Secondary hyperparathyroidism: Increased PTH production due to chronic kidney disease or vitamin D deficiency
  • Suppressed PTH
    • Hypoparathyroidism: Insufficient PTH production leading to hypocalcemia
    • Surgical removal or autoimmune destruction of the parathyroid glands
    • Evaluate in conjunction with calcium and vitamin D measurements

Gonadal Hormone Interpretation

Testosterone

  • Normal
    • Varies depending on age and sex
    • Adult males: 300-1000 ng/dL
    • Adult females: 15-70 ng/dL
  • Elevated Testosterone
    • Polycystic ovary syndrome (PCOS) in women: Hirsutism, acne, and menstrual irregularities
    • Testicular tumor in men: Rare
    • Congenital adrenal hyperplasia (CAH): Genetic defect in cortisol synthesis
  • Suppressed Testosterone
    • Hypogonadism in men: Sexual dysfunction, decreased muscle mass, and fatigue
    • Klinefelter syndrome: Genetic disorder in males (XXY)
    • Pituitary or hypothalamic dysfunction: Secondary hypogonadism
    • Anabolic steroid use: Suppression of endogenous testosterone production

Estradiol (E2)

  • Normal
    • Varies depending on sex and menstrual cycle phase in women
    • Adult females: 30-400 pg/mL (varies with cycle)
    • Adult males: 10-40 pg/mL
  • Elevated Estradiol
    • Ovarian tumor in women: Rare
    • Gynecomastia in men: Enlargement of breast tissue
    • Precocious puberty: Early onset of puberty in children
  • Suppressed Estradiol
    • Hypogonadism in women: Menopause or Turner syndrome
    • Pituitary or hypothalamic dysfunction: Secondary hypogonadism
    • Symptoms: Amenorrhea, infertility, and osteoporosis

Progesterone

  • Normal
    • Varies depending on menstrual cycle phase and pregnancy
  • Elevated Progesterone
    • Pregnancy: Physiological increase
    • Ovarian cyst or tumor: Rare
  • Suppressed Progesterone
    • Anovulation: Failure to ovulate
    • Luteal phase defect: Inadequate progesterone production after ovulation

Other Hormones

Insulin

  • Normal
    • Fasting insulin: 3-17 μIU/mL (may vary by assay)
  • Elevated Insulin
    • Insulin resistance: Elevated insulin levels required to maintain normal glucose levels
    • Insulinoma: Insulin-secreting tumor in the pancreas
    • Type 2 diabetes: Early stages
  • Suppressed Insulin
    • Type 1 diabetes: Autoimmune destruction of pancreatic beta cells
    • Pancreatic damage or removal

C-Peptide

  • Normal
    • C-peptide: 0.5-2.0 ng/mL (may vary by assay)
  • Elevated C-Peptide
    • Insulinoma: Insulin-secreting tumor in the pancreas
    • Insulin resistance: Elevated insulin production
    • Type 2 diabetes: Early stages
  • Suppressed C-Peptide
    • Type 1 diabetes: Autoimmune destruction of pancreatic beta cells
    • Exogenous insulin administration: Suppression of endogenous insulin production
    • Factitious hypoglycemia: Intentional insulin administration

Human Chorionic Gonadotropin (hCG)

  • Normal
    • Non-pregnant: < 5 mIU/mL
    • Pregnancy: Rapidly increases in early pregnancy
  • Elevated hCG
    • Pregnancy: Confirms pregnancy
    • Ectopic pregnancy: Elevated hCG, but lower than expected for gestational age
    • Gestational trophoblastic disease (e.g., hydatidiform mole): Markedly elevated hCG levels
    • Tumor marker for certain cancers (e.g., testicular cancer)
  • Suppressed hCG
    • Non-pregnant: Normal
    • Miscarriage: Decreasing hCG levels

Key Terms

  • Reference Interval: The range of values found in healthy individuals
  • Clinical Context: The patient’s clinical history, physical examination findings, and other laboratory data
  • Interfering Substance: A substance that affects the accuracy of a test
  • Assay Limitation: The limitations of the specific assay used, including its sensitivity, specificity, and potential for cross-reactivity
  • Hormone Excess: Abnormally high hormone levels
  • Hormone Deficiency: Abnormally low hormone levels
  • Primary Endocrine Disorder: A disorder originating in the endocrine gland itself
  • Secondary Endocrine Disorder: A disorder resulting from dysfunction of the pituitary or hypothalamus
  • Tertiary Endocrine Disorder: A disorder resulting from dysfunction of the hypothalamus
  • Stimulation Test: A test used to assess hormone deficiency by stimulating hormone release
  • Suppression Test: A test used to assess hormone excess by suppressing hormone production