Hormone Panels

Hormone panels are groups of laboratory measurements used to evaluate endocrine function. They can include hormones produced directly by endocrine glands, regulatory hormones produced by the hypothalamus or pituitary gland, hormone-binding proteins, metabolites, electrolytes, and other biochemical markers influenced by endocrine activity.

Endocrine laboratory testing differs from many other forms of blood testing because hormone concentrations must usually be interpreted as part of a regulatory axis. A hormone concentration that appears normal in isolation may be inappropriate when the concentration of its controlling hormone or target-gland hormone is considered.

For example, thyroid function is commonly evaluated by examining thyroid-stimulating hormone (TSH) together with free thyroxine (free T4). A low free T4 concentration accompanied by elevated TSH suggests a different anatomical level of dysfunction from a low free T4 accompanied by an inappropriately low or normal TSH.

Purpose of Hormone Testing

Hormone testing can help determine whether an endocrine gland is producing too much or too little hormone and whether an abnormality originates within the target endocrine gland or within its regulatory pathways.

Major uses include:

• Evaluation of suspected hormone deficiency
• Evaluation of suspected hormone excess
• Localization of dysfunction within an endocrine axis
• Assessment of reproductive function
• Evaluation of metabolic abnormalities
• Monitoring of endocrine disorders
• Monitoring of hormone replacement or suppressive therapy
• Assessment of treatment response

Endocrine Axes

Many endocrine systems are organized into hierarchical regulatory pathways involving the hypothalamus, pituitary gland, and a peripheral endocrine organ.

Important examples include:

• Hypothalamic-pituitary-thyroid axis
• Hypothalamic-pituitary-adrenal axis
• Hypothalamic-pituitary-gonadal axis
• Growth hormone and IGF-1 axis

Negative Feedback

Negative feedback is fundamental to interpretation of many hormone panels.

Hormones produced by peripheral endocrine glands commonly suppress further stimulation from the hypothalamus and pituitary. When peripheral hormone production falls, regulatory hormone concentrations may rise. When peripheral hormone production becomes excessive, regulatory hormone concentrations may fall.

Primary and Central Endocrine Disorders

Hormone measurements can help distinguish disease of a peripheral endocrine gland from disease affecting its central regulatory pathway.

Pattern	General Interpretation
Low target hormone + high stimulating hormone	Suggests primary failure of the target endocrine gland
Low target hormone + low or inappropriately normal stimulating hormone	Suggests central regulatory dysfunction
High target hormone + suppressed stimulating hormone	Can suggest autonomous or primary target-gland hormone excess

Thyroid Hormone Panel

Thyroid laboratory testing evaluates the hypothalamic-pituitary-thyroid axis.

Common measurements include TSH and free T4, with additional tests used according to the clinical question.

Thyroid-Stimulating Hormone

TSH is secreted by thyrotroph cells of the anterior pituitary and stimulates thyroid follicular cells.

It is particularly useful for evaluating primary thyroid dysfunction because pituitary TSH secretion responds sensitively to changes in circulating thyroid hormone activity.

Free T4

Free T4 represents the unbound fraction of circulating thyroxine available to tissues.

It is an important measurement when assessing the amount of circulating thyroid hormone and is especially useful when pituitary or hypothalamic disease is suspected.

Free T3

Free T3 or total T3 can be measured in selected clinical situations.

T3 testing can be particularly useful in evaluation of suspected hyperthyroidism when T4 concentrations do not fully explain the biochemical findings.

Typical Thyroid Patterns

Condition	TSH	Free T4
Primary hypothyroidism	High	Low
Primary hyperthyroidism	Low	High in overt disease
Central hypothyroidism	Low or inappropriately normal, sometimes mildly elevated	Low
Subclinical hypothyroidism	High	Within reference range
Subclinical hyperthyroidism	Low	Within reference range

Thyroid Autoantibodies

Antibody testing can help identify autoimmune thyroid disease.

Common measurements include:

• Thyroid peroxidase antibodies
• Thyroglobulin antibodies
• TSH receptor antibodies

Thyroid Peroxidase Antibodies

Thyroid peroxidase antibodies are frequently associated with autoimmune thyroiditis.

They provide information about thyroid autoimmunity rather than directly measuring thyroid hormone production.

TSH Receptor Antibodies

Antibodies directed against the TSH receptor can stimulate or alter receptor activity.

Stimulating TSH receptor antibodies are important in the pathophysiology of Graves disease.

Adrenal Hormone Panel

Evaluation of adrenal function can involve hormones from both the adrenal cortex and adrenal medulla.

Testing is selected according to whether glucocorticoid, mineralocorticoid, androgen, or catecholamine abnormalities are suspected.

Cortisol

Cortisol is the principal glucocorticoid produced by the adrenal cortex.

Its concentration varies according to circadian rhythm, physiological stress, illness, medications, and other factors, so timing and clinical context are important.

ACTH

Adrenocorticotropic hormone (ACTH) is produced by corticotroph cells of the anterior pituitary and stimulates cortisol production by the adrenal cortex.

Measurement of ACTH together with cortisol can help localize abnormalities within the hypothalamic-pituitary-adrenal axis.

Primary Adrenal Insufficiency

In primary adrenal insufficiency, the adrenal cortex cannot produce adequate cortisol despite pituitary stimulation.

The typical hormonal pattern is low cortisol with elevated ACTH.

Central Adrenal Insufficiency

When adrenal insufficiency results from inadequate pituitary ACTH secretion, cortisol is low while ACTH is low or inappropriately normal.

Mineralocorticoid function is generally better preserved because aldosterone is regulated primarily through the renin-angiotensin system and extracellular potassium concentration.

Morning Cortisol

Cortisol concentrations normally vary over the day and are generally highest around the early morning and awakening period.

Morning cortisol measurements can therefore provide useful initial information when adrenal insufficiency is suspected, although dynamic testing may be necessary when results are indeterminate.

ACTH Stimulation Test

The ACTH stimulation test evaluates adrenal cortisol production after administration of synthetic ACTH.

Cortisol is measured before and after stimulation, and an inadequate response can support a diagnosis of adrenal insufficiency when interpreted using appropriate assay-specific criteria.

Cortisol Excess

Evaluation of suspected endogenous cortisol excess requires tests designed to identify loss of normal cortisol regulation rather than reliance on a single random cortisol measurement.

Common approaches include assessment of late-night cortisol, urinary free cortisol, or suppression of cortisol after dexamethasone administration.

Dexamethasone Suppression Testing

Dexamethasone is a synthetic glucocorticoid that normally suppresses pituitary ACTH secretion and therefore decreases endogenous cortisol production.

Failure of appropriate cortisol suppression can provide evidence of abnormal regulation of the hypothalamic-pituitary-adrenal axis.

Aldosterone and Renin

Aldosterone is produced by the zona glomerulosa of the adrenal cortex and promotes renal sodium retention and potassium excretion.

Renin is released by juxtaglomerular cells of the kidney and initiates the renin-angiotensin-aldosterone system.

Aldosterone-Renin Relationship

Aldosterone and renin are commonly interpreted together rather than independently.

In autonomous primary aldosterone excess, aldosterone secretion is relatively inappropriate while renin activity or concentration becomes suppressed.

Aldosterone-Renin Ratio

The aldosterone-renin ratio is used as a screening approach for primary aldosteronism in appropriate clinical settings.

Interpretation can be influenced by medications, sodium intake, potassium status, posture, collection conditions, and laboratory methodology.

Adrenal Androgens

The adrenal cortex produces androgen precursors including dehydroepiandrosterone (DHEA) and its sulfated form DHEA-S.

DHEA-S measurement can be useful when investigating selected disorders of androgen excess.

Catecholamine Testing

The adrenal medulla produces catecholamines, particularly epinephrine and norepinephrine.

Biochemical evaluation of suspected catecholamine-producing tumors commonly focuses on catecholamine metabolites rather than isolated random catecholamine concentrations.

Metanephrines

Metanephrine and normetanephrine are metabolites of catecholamines.

Plasma free metanephrines or urinary fractionated metanephrines can be used in evaluation of suspected pheochromocytoma or paraganglioma.

Pituitary Hormone Panel

The anterior pituitary produces several hormones that regulate peripheral endocrine glands and other tissues.

A pituitary evaluation can include measurements from several endocrine axes when generalized pituitary dysfunction is suspected.

Major Anterior Pituitary Hormones

Hormone	Major Target
TSH	Thyroid gland
ACTH	Adrenal cortex
LH	Gonads
FSH	Gonads
Growth hormone	Multiple tissues, partly through IGF-1
Prolactin	Mammary glands and reproductive regulatory pathways

Prolactin

Prolactin is produced by lactotroph cells of the anterior pituitary.

Its secretion is unusual among anterior pituitary hormones because it is under strong tonic inhibitory control by hypothalamic dopamine.

Hyperprolactinemia

Elevated prolactin can occur because of a prolactin-secreting pituitary tumor, interruption of hypothalamic dopamine signaling, selected medications, hypothyroidism, pregnancy, and other physiological or pathological conditions.

Persistent hyperprolactinemia can suppress normal hypothalamic-pituitary-gonadal function.

Growth Hormone

Growth hormone (GH) is secreted by somatotroph cells of the anterior pituitary.

Its secretion is pulsatile, making isolated random GH concentrations difficult to interpret in many clinical situations.

Insulin-Like Growth Factor 1

Insulin-like growth factor 1 (IGF-1) is produced largely by the liver in response to growth hormone stimulation.

Because circulating IGF-1 concentrations are more stable than pulsatile GH concentrations, IGF-1 is useful in evaluating disorders of growth hormone excess or deficiency.

Growth Hormone Suppression Testing

Glucose normally suppresses growth hormone secretion.

Failure of appropriate GH suppression following an oral glucose load can support the diagnosis of growth hormone excess when interpreted with IGF-1 and clinical findings.

Growth Hormone Stimulation Testing

Because growth hormone secretion is naturally pulsatile, a low random GH measurement does not reliably establish growth hormone deficiency.

Dynamic stimulation testing can therefore be required when clinically significant GH deficiency is suspected.

Gonadal Hormone Panels

Evaluation of reproductive endocrine function commonly involves the hypothalamic-pituitary-gonadal axis.

Tests can include LH, FSH, estradiol, testosterone, progesterone, SHBG, and other hormones according to the clinical question.

Luteinizing Hormone

LH is secreted by gonadotroph cells of the anterior pituitary.

In the ovaries, LH stimulates theca cell androgen production and participates in ovulation and corpus luteum formation. In the testes, LH stimulates Leydig cell testosterone production.

Follicle-Stimulating Hormone

FSH is also produced by anterior pituitary gonadotroph cells.

It promotes ovarian follicular development and granulosa cell function in females and supports Sertoli cell function and spermatogenesis in males.

Estradiol

Estradiol is an important estrogen produced predominantly by the ovaries in premenopausal women.

Its concentration changes substantially during the menstrual cycle and must therefore be interpreted according to physiological context.

Progesterone

Progesterone is produced in substantial amounts by the corpus luteum after ovulation and by the placenta during pregnancy.

Measurement during an appropriately timed portion of the menstrual cycle can provide information about whether ovulation has occurred.

Testosterone

Testosterone is produced primarily by testicular Leydig cells in males and in smaller quantities by the ovaries and adrenal steroid pathways in females.

Measurement can be useful in evaluation of hypogonadism, androgen excess, and selected reproductive endocrine disorders.

Sex Hormone-Binding Globulin

Sex hormone-binding globulin (SHBG) is a circulating protein produced primarily by the liver that binds testosterone and estradiol.

Changes in SHBG concentration can substantially affect total hormone concentrations and the proportion of hormone that is biologically available.

Primary Hypogonadism

When the gonads fail to produce adequate sex steroids, negative feedback to the hypothalamus and pituitary decreases.

This can produce increased LH and FSH concentrations, a pattern called hypergonadotropic hypogonadism.

Central Hypogonadism

Hypothalamic or pituitary dysfunction can cause inadequate gonadotropin secretion.

Sex steroid concentrations become low while LH and FSH are low or inappropriately normal, producing hypogonadotropic hypogonadism.

Ovarian Reserve Testing

Selected hormone measurements can provide information related to ovarian follicular reserve.

Tests can include anti-Müllerian hormone and, in appropriate contexts, FSH and estradiol measurements.

Anti-Müllerian Hormone

Anti-Müllerian hormone (AMH) is produced by granulosa cells of developing ovarian follicles.

Its concentration reflects aspects of the population of growing follicles and is used in reproductive medicine as a marker related to ovarian reserve.

PCOS Hormone Testing

Laboratory evaluation of suspected polycystic ovary syndrome can include measurements related to androgen excess and exclusion of alternative endocrine disorders.

Potential tests include testosterone, SHBG, DHEA-S, TSH, prolactin, and selected adrenal steroid measurements depending on the presentation.

Pancreatic Hormone and Glucose Testing

The endocrine pancreas regulates glucose metabolism primarily through insulin and glucagon.

Clinical laboratory evaluation commonly focuses on glucose regulation and pancreatic beta-cell function.

Fasting Plasma Glucose

Fasting plasma glucose measures circulating glucose after an appropriate period without caloric intake.

It is commonly used in assessment of diabetes mellitus and disorders of glucose regulation.

Hemoglobin A1c

Hemoglobin A1c (HbA1c) reflects glycation of hemoglobin and provides information about average glycemic exposure over the preceding several months.

Conditions affecting erythrocyte lifespan or hemoglobin composition can alter its interpretation.

Oral Glucose Tolerance Test

The oral glucose tolerance test measures the physiological response to a standardized oral glucose load.

It can be used in selected diagnostic settings involving diabetes, gestational diabetes, and other abnormalities of glucose regulation.

Insulin

Circulating insulin can be measured when evaluating selected disorders of insulin secretion, hypoglycemia, or metabolic function.

Insulin concentrations must be interpreted in relation to the concurrent glucose concentration and clinical setting.

C-Peptide

Insulin and C-peptide are released together when pancreatic beta cells process proinsulin.

C-peptide therefore provides information about endogenous insulin secretion.

Insulin and C-Peptide

Measurement	Major Significance
Insulin	Includes endogenous insulin and can include administered insulin depending on the assay
C-peptide	Reflects endogenous beta-cell insulin secretion

Hypoglycemia Evaluation

When clinically significant hypoglycemia is being investigated, several measurements can be obtained during the low-glucose episode.

Depending on the clinical context, these can include glucose, insulin, C-peptide, proinsulin, beta-hydroxybutyrate, and screening for medications capable of producing hypoglycemia.

Parathyroid Hormone Panel

The parathyroid glands play a central role in regulation of extracellular calcium and phosphate concentrations.

Parathyroid hormone must therefore be interpreted together with calcium and related biochemical measurements.

Parathyroid Hormone

Parathyroid hormone (PTH) is produced by chief cells of the parathyroid glands.

Its secretion increases when extracellular ionized calcium decreases and is suppressed when calcium rises.

Calcium

Serum calcium exists in ionized, protein-bound, and complexed forms.

Ionized calcium is the physiologically active fraction, while total calcium is commonly measured in routine laboratory testing.

Albumin and Total Calcium

A substantial proportion of circulating calcium is bound to albumin.

Changes in albumin concentration can therefore alter total serum calcium without producing an equivalent change in ionized calcium.

Phosphate

PTH influences phosphate handling by the kidneys, promoting urinary phosphate excretion.

Serum phosphate measurement can therefore provide useful complementary information when evaluating parathyroid disorders.

Vitamin D

Vitamin D physiology is closely related to calcium and parathyroid function.

25-hydroxyvitamin D is commonly measured to assess vitamin D status, while the kidney converts it to biologically active 1,25-dihydroxyvitamin D under hormonal regulation.

Primary Hyperparathyroidism

In primary hyperparathyroidism, PTH secretion is excessive or inappropriate relative to the serum calcium concentration.

A typical pattern includes elevated calcium with an elevated or inappropriately nonsuppressed PTH concentration.

Secondary Hyperparathyroidism

Secondary hyperparathyroidism occurs when chronic physiological stimuli increase PTH secretion.

Potential causes include chronic kidney disease and vitamin D deficiency, with laboratory patterns depending on the underlying disorder.

Calcium-PTH Relationship

Finding	Interpretive Principle
High calcium + high or nonsuppressed PTH	Suggests PTH-dependent hypercalcemia
High calcium + suppressed PTH	Suggests a non-PTH-mediated cause of hypercalcemia
Low calcium + elevated PTH	Can represent an appropriate compensatory response
Low calcium + low PTH	Can suggest inadequate parathyroid hormone secretion

Dynamic Endocrine Testing

A single hormone measurement does not always adequately assess endocrine function because many hormones are secreted episodically, vary throughout the day, or respond dynamically to physiological stimuli.

Dynamic tests intentionally stimulate or suppress an endocrine pathway and measure the resulting hormonal response.

Stimulation Tests

Stimulation tests evaluate whether an endocrine gland can increase hormone production when appropriately challenged.

The ACTH stimulation test is an important example.

Suppression Tests

Suppression tests determine whether hormone secretion decreases appropriately after administration of a physiological or pharmacological suppressive stimulus.

Dexamethasone suppression testing for cortisol regulation and glucose suppression testing for growth hormone are examples.

Common Dynamic Tests

Test	Axis Evaluated	General Purpose
ACTH stimulation	Adrenal	Assess cortisol-producing capacity
Dexamethasone suppression	HPA axis	Assess suppressibility of cortisol production
Oral glucose suppression of GH	Growth hormone axis	Assess inappropriate GH secretion
GH stimulation testing	Growth hormone axis	Assess reserve when GH deficiency is suspected

Circadian Rhythms

Some endocrine hormones follow predictable daily rhythms.

Cortisol is an important example, with concentrations normally varying substantially across the day.

Timing of specimen collection can therefore be essential for meaningful interpretation.

Pulsatile Hormone Secretion

Hormones such as growth hormone, LH, and ACTH can be released in pulses.

A single random measurement may therefore represent only one moment within a fluctuating secretory pattern.

Menstrual Cycle Variation

Reproductive hormones vary substantially during the menstrual cycle.

LH, FSH, estradiol, and progesterone results must often be interpreted according to menstrual phase and the clinical question being investigated.

Pregnancy

Pregnancy causes major physiological changes in endocrine function, hormone-binding proteins, and hormone concentrations.

Pregnancy-specific reference ranges or interpretive approaches may therefore be required for selected tests.

Hormone-Binding Proteins

Many hormones circulate partly bound to plasma proteins.

Changes in these binding proteins can alter total hormone concentrations without producing an equivalent change in the free biologically active fraction.

Thyroxine-Binding Globulin

Thyroxine-binding globulin binds much of the circulating T4 and T3.

Changes in its concentration can alter total thyroid hormone measurements even when free hormone concentrations remain physiologically appropriate.

Cortisol-Binding Globulin

Much of circulating cortisol is bound to cortisol-binding globulin and albumin.

Changes in binding proteins can therefore influence total serum cortisol measurements.

Reference Ranges

Hormone results are interpreted using laboratory-specific reference intervals.

Reference ranges can vary according to assay methodology, population, age, sex, physiological state, specimen timing, and other factors.

Assay Methods

Hormones can be measured using several laboratory technologies, including immunoassays and mass spectrometry-based methods.

Different methods can produce different analytical characteristics, making assay-specific interpretation important.

Immunoassays

Immunoassays use antibodies to detect and quantify specific hormones or related molecules.

They are widely used because they can be automated and applied to many endocrine analytes.

Mass Spectrometry

Mass spectrometry can provide highly specific measurement of selected steroid hormones and other endocrine analytes.

It is particularly valuable when accurate differentiation of structurally related molecules is required.

Factors Affecting Hormone Results

Hormone measurements can be influenced by physiological, pharmacological, and analytical factors.

Important considerations include:

• Time of day
• Fasting status
• Menstrual cycle phase
• Pregnancy
• Acute illness
• Physiological stress
• Medications
• Hormone-binding proteins
• Kidney or liver function
• Assay methodology

Medication Effects

Medications can alter endocrine laboratory results by changing hormone synthesis, secretion, metabolism, binding, or assay measurement.

Medication history is therefore an important part of endocrine test interpretation.

Biotin Interference

High-dose biotin supplementation can interfere with certain immunoassay systems and produce misleading endocrine laboratory results.

The direction and magnitude of interference depend on the design of the specific assay.

Acute Illness

Severe illness can alter multiple endocrine axes even when the endocrine glands themselves are not primarily diseased.

Laboratory abnormalities obtained during acute illness must therefore be interpreted carefully within the clinical context.

Common Endocrine Panels

Panel or Axis	Common Measurements
Thyroid	TSH, free T4, sometimes T3 and thyroid antibodies
Adrenal glucocorticoid	Cortisol, ACTH and dynamic testing when indicated
Mineralocorticoid	Aldosterone, renin, potassium and related measurements
Pituitary	Prolactin, TSH, ACTH, LH, FSH, IGF-1 and target-gland hormones
Gonadal	LH, FSH, estradiol, progesterone, testosterone, SHBG and selected additional tests
Pancreatic/glucose	Glucose, HbA1c, insulin and C-peptide when indicated
Parathyroid/calcium	PTH, calcium, phosphate, albumin and vitamin D-related measurements

Hormone Panels and Imaging

Biochemical testing and endocrine imaging serve complementary roles.

Hormone measurements establish whether an endocrine pathway is functioning abnormally, while imaging can identify and localize structural lesions responsible for selected abnormalities.

Biochemical Diagnosis Before Localization

For several endocrine disorders, biochemical evidence of hormone excess or deficiency is established before attempting to localize a responsible lesion.

This approach is particularly important because incidental structural abnormalities are common and may not be responsible for the hormonal disorder being investigated.

Incidentalomas and Hormone Testing

An endocrine mass discovered incidentally can require biochemical evaluation to determine whether it produces hormones autonomously.

Examples include adrenal and pituitary incidentalomas, where structural findings and endocrine function must be considered together.

Interpreting Hormone Panels

Hormone panel interpretation requires more than comparing individual numbers with reference intervals.

The relationship between hormones often provides the most useful physiological information.

Examples of Paired Interpretation

Hormones	Physiological Relationship
TSH and free T4	Pituitary stimulation and thyroid hormone production
ACTH and cortisol	Pituitary stimulation and adrenal glucocorticoid production
LH/FSH and sex steroids	Pituitary stimulation and gonadal function
PTH and calcium	Parathyroid response to extracellular calcium
Renin and aldosterone	Renin-angiotensin regulation of mineralocorticoid secretion
Insulin/C-peptide and glucose	Beta-cell secretion relative to glycemic state

Key Features of Hormone Panels

Feature	Key Point
Primary purpose	Assessment of endocrine function
Interpretive principle	Hormones should be interpreted within their regulatory axes
Negative feedback	Helps localize primary versus central endocrine dysfunction
Thyroid panel	Commonly centers on TSH and free T4
Adrenal evaluation	Can include cortisol, ACTH, aldosterone, renin and adrenal androgen testing
Pituitary evaluation	Requires assessment of pituitary hormones together with target-gland hormones
Gonadal evaluation	Can include LH, FSH and sex steroid measurements
Parathyroid evaluation	PTH must be interpreted in relation to calcium
Dynamic testing	Assesses endocrine response to stimulation or suppression
Timing	Important for hormones with circadian, pulsatile or cyclic secretion

Anatomical and Physiological Importance

Hormone panels provide a functional map of the endocrine system. Although endocrine glands are anatomically separated throughout the body, they communicate through circulating hormones and organized feedback pathways. Measuring hormones at different levels of these pathways can help identify where endocrine dysfunction originates.

The thyroid axis provides a clear example. When the thyroid gland fails, circulating thyroid hormone decreases and pituitary TSH rises because negative feedback has been lost. If the pituitary fails instead, thyroid hormone can decrease without an appropriate increase in TSH. The same principle can be applied to the adrenal and gonadal axes.

Endocrine laboratory interpretation therefore connects anatomy directly with physiology. Hormone concentrations can indicate whether dysfunction lies within the thyroid gland, adrenal cortex, gonads, pituitary gland, or another component of a regulatory pathway, while imaging can subsequently provide structural information when localization is required.

For this reason, endocrine diagnosis often depends not on a single hormone value but on the relationship among multiple measurements, their timing, the patient's physiological state, and the anatomy of the endocrine axis being investigated.