Assessing the endocrine system involves a combination of physical examination, blood and saliva tests, and imaging studies. Because hormones regulate nearly every process in the body, from metabolism to blood sugar to stress response, no single test captures the full picture. Instead, assessment follows a logical sequence: look for visible signs of hormonal imbalance, confirm with targeted lab work, and use imaging when a structural problem is suspected.
Physical Examination Still Comes First
A hands-on exam remains one of the most valuable first steps in identifying endocrine problems, particularly for the thyroid gland. Palpating the neck can reveal an enlarged thyroid (goiter), which, when paired with the patient’s symptoms, raises suspicion for either an underactive or overactive gland. A single firm, hard nodule, especially with swollen lymph nodes nearby, raises concern for thyroid cancer. Multiple nodules in someone with signs of an overactive thyroid point toward toxic multinodular goiter instead.
A painful, swollen thyroid in someone with fever and early signs of an overactive gland suggests subacute thyroiditis, an inflammatory condition. A painless, movable lump along the midline of the neck that shifts when the tongue sticks out is characteristic of a thyroglossal duct cyst, most often found below the hyoid bone.
One useful bedside test is Pemberton’s sign. The patient raises both arms overhead, and the examiner watches for facial flushing and difficulty breathing. A positive result suggests an enlarged thyroid extending into the chest cavity, compressing veins and the windpipe. Another physical clue is pretibial myxedema, a thickening of the skin over the shins that is strongly associated with Graves’ disease.
Beyond the thyroid, a broader physical exam looks for patterns that suggest hormonal excess or deficiency: changes in skin texture and thickness, unusual fat distribution (particularly across the upper back and face), abnormal hair growth or loss, stretch marks, and shifts in body proportions. These visible signs guide which laboratory tests to order next.
Baseline Blood Tests for Major Glands
Most endocrine assessments start with a simple blood draw targeting the gland in question. The results determine whether further, more specialized testing is needed.
Thyroid
Thyroid-stimulating hormone (TSH) is the single most useful screening test for thyroid function. The standard reference range is 0.3 to 4.0 mU/L. A high TSH signals an underactive thyroid; a low TSH signals an overactive one. When TSH is abnormal, free T4 (normal range: 0.7 to 2.1 ng/dL) and total T3 (normal range: 75 to 175 ng/dL) are measured to gauge severity and clarify the pattern. For example, a suppressed TSH with an elevated free T4 confirms overt hyperthyroidism, while a suppressed TSH with normal T4 and T3 levels indicates a milder, subclinical form.
Adrenal Glands
A morning serum cortisol, drawn within three hours of waking (typically between 6 and 9 AM), is the standard starting point for suspected adrenal insufficiency. When clinical suspicion is high, particularly if someone has low blood pressure upon standing along with other symptoms, cortisol, ACTH, renin, and aldosterone are all drawn at the same time to speed up the diagnosis. ACTH levels then distinguish between primary adrenal insufficiency (where the adrenal glands themselves are failing, producing high ACTH) and secondary insufficiency (where the pituitary gland isn’t sending adequate signals, producing low ACTH). Elevated potassium on a basic metabolic panel only appears in primary adrenal insufficiency, since the body’s aldosterone regulation system remains intact when the problem originates in the pituitary.
Pituitary Gland
The pituitary is assessed indirectly through the hormones it controls. FSH and LH evaluate reproductive function. TSH evaluates thyroid regulation. ACTH evaluates adrenal regulation. Growth hormone and prolactin can be measured directly. An abnormal result in any downstream gland always raises the question of whether the problem originates in the gland itself or in the pituitary’s signaling.
Blood Sugar Regulation
For the pancreas and insulin function, the two primary screening tools are fasting blood glucose (requiring at least an 8-hour fast) and hemoglobin A1C, which reflects average blood sugar over the previous two to three months. An A1C below 5.7% is normal. Between 5.7% and 6.4% indicates prediabetes. At 6.5% or higher, the result meets the threshold for diabetes. A1C does not require fasting, making it a convenient option.
When Timing and Preparation Matter
Hormones don’t stay at the same level throughout the day, and poor preparation before testing is one of the most common reasons for misleading results. Cortisol peaks in the early morning and drops to its lowest at night. Testosterone follows a similar pattern. Both should be drawn between 8 and 10 AM, or as close to waking as possible, to capture their highest and most diagnostically useful levels.
Aldosterone and renin also fluctuate with daily rhythms and body position. A mid-morning collection is recommended, and the lab should note whether the sample was taken while the patient was upright or lying down, since posture changes the result.
Fasting for 10 to 12 hours before a glucose test minimizes variability, but prolonged fasting beyond 16 hours can actually produce a false positive on a glucose tolerance test. Fasting for routine cholesterol panels is no longer considered necessary, as the changes after eating are clinically insignificant for most people. Patients should avoid restricting water while fasting, especially older adults, since dehydration can skew certain results and increase the risk of dizziness.
Medications also interfere with hormone levels. Oral estrogen and corticosteroids both alter cortisol measurements, and several common medications affect aldosterone readings. Clinicians typically ask patients to stop or adjust specific medications before testing, depending on what’s being measured.
Dynamic Stimulation and Suppression Tests
When baseline blood tests fall in a gray zone, dynamic tests push the system to see how it responds. These are the endocrine equivalent of a stress test for the heart: rather than measuring a hormone at rest, they challenge the gland to perform and see whether its response is normal.
The ACTH stimulation test evaluates whether the adrenal glands can produce cortisol on demand. A synthetic form of ACTH is injected, and cortisol levels are measured at 30 and 60 minutes. A cortisol level reaching 18 or above at 30 minutes is considered a normal response. A baseline cortisol below 5 combined with ACTH levels above 100 is usually diagnostic of primary adrenal insufficiency without needing further testing.
The dexamethasone suppression test works in the opposite direction, screening for excess cortisol production (Cushing’s syndrome). The patient takes a small dose of a synthetic steroid at 11 PM, and cortisol is measured the next morning by 8 AM. In a healthy person, the synthetic steroid tells the brain to stop producing its own cortisol, dropping levels below 1.8. If cortisol stays above 10, the likelihood of Cushing’s syndrome is high. Higher-dose versions of this test help distinguish between different causes of cortisol excess once the initial screen is positive.
Salivary and Urine Testing
Not all hormone testing requires a blood draw. Late-night salivary cortisol has become a preferred initial screening test for Cushing’s syndrome. The collection is simple: the patient provides a saliva sample around midnight at home. This avoids the practical difficulty of getting an unstressed blood draw late at night in a hospital setting, which itself can raise cortisol and muddy the results. Salivary cortisol is unaffected by body weight or by variations in the binding proteins that can throw off blood measurements, making it a more reliable reflection of what’s actually circulating.
Salivary testing also appears to detect recurrence of Cushing’s disease after surgery earlier than urine-based testing, which makes it useful for long-term follow-up. Twenty-four-hour urine collections remain an option for measuring total cortisol output over a full day but are less convenient and more prone to collection errors.
Imaging the Endocrine Glands
Imaging enters the assessment when lab work confirms a hormonal abnormality and the next step is identifying the structural cause.
For the pituitary gland, MRI is the preferred study. It provides the detail needed to identify small tumors (pituitary adenomas) that may be only a few millimeters across. For the adrenal glands, both CT and MRI are equally effective at detecting tumors. CT is more commonly used as a first-line study because of its availability and speed, while MRI adds value when a mass needs further characterization.
Thyroid imaging relies primarily on ultrasound and nuclear medicine scans. Ultrasound shows the size, shape, and internal structure of nodules and can distinguish fluid-filled cysts from solid masses, something physical examination alone cannot do. Nuclear medicine scans (using a small amount of radioactive iodine or similar tracer) reveal whether a nodule is actively producing thyroid hormone (“hot”) or not (“cold”), which affects the likelihood of cancer and guides the decision about whether a biopsy is needed.
Putting the Assessment Together
A complete endocrine assessment moves through a predictable sequence. Symptoms and physical findings suggest which gland is involved. Baseline blood tests, drawn at the right time of day with proper preparation, confirm or rule out a hormonal abnormality. If results are borderline, dynamic testing clarifies whether the gland is truly failing or overproducing. Once a biochemical diagnosis is established, imaging identifies the structural source. At each stage, the results from the previous step determine what comes next, making endocrine assessment less of a blanket screening process and more of a focused, stepwise investigation guided by clinical clues.