Venous blood test for leptin

In order to be able to adjust the level of leptin, the hormone responsible for the feeling of satiety, we need to know its quantitative characteristics. In other words, its concentration in the bloodstream. There is only one way to do this – to take blood for analysis and evaluate it. From the article you will learn how it is done, what are the indications for the test, how it is evaluated.

Contents:

1. Once again about leptin.
2. Indications and contraindications for the test.
3. Blood Collection Preparation and Testing.
4. Normal values.
5. Results Assessment.

Once again about leptin

Leptin is a steroid that is involved in energy, neuroendocrine metabolism, and body weight control. Most of the bioactive substance receptors are localized in the hypothalamic centers that produce peptide hormones. In addition to leptin, these same receptors affect the production of pituitary steroids, which help it control normal puberty and growth.

The hormone simultaneously affects the receptors of hypothalamic centers that synthesize neuropeptide Y. As a result, the synthesis of antagonists is minimized, which changes the appetite and the frequency of meals. Unfortunately, this situation can provoke hormonal malfunctions in adolescents: for example, amenorrhea. With weight gain from overeating, the concentration of leptin in serum increases. The hormone balances metabolism and leads to weight loss by minimizing feelings of hunger, rapid degradation of lipids and glycogen synthesis in muscles.

Leptin synthesis is increased under the influence of estrogen and blocked by testosterone, so the concentration of the bioactive substance is higher in women than in men. Leptin levels are correlated during the day: in the morning and late evening there is a lot of it, during the day it is less. The amount of inactive hormone reaches 75%. It is believed that the main function of leptin is the prevention of lipotoxicosis in case of overeating.

This is a condition in which there is ectopic deposition of fat in the tissues of the body, which normally lipocytes do not deposit. It is leptin that protects against accumulated fat reserves in the periphery, which helps prevent obesity. Leptin analysis is widely used in cardiology practice, endocrinology, gynecology and dietetics. But most importantly, it is the basis for diagnosing obesity, type 2 diabetes and amenorrhea.

Indications and contraindications for the test

Venous blood sampling for leptin level analysis is performed according to the indications:

• detection of hereditary insufficiency of the hormone;
• differential diagnosis of obesity and type 2 diabetes mellitus;
• unusual activity of the reproductive system as a result of starvation or high physical activity;
• recurrent thrombosis;
• use in the treatment of glucocorticoids, replacement therapy for impaired thyroid function;
• use of hormonal contraceptives.

There is an association between leptin levels and cardiovascular abnormalities, so the test is taken in patients with such problems. A contraindication to the test is considered to be non-compliance with the diet before blood sampling: too dense and frequent satisfaction of hunger, dieting or starvation, as well as physical hyperexertion.

Blood Collection Preparation and Testing

Blood is taken from a vein to perform the test. Before the biomaterial is taken, the patient is advised to strictly follow certain rules:

1. The interval between meals should be more than 12 hours.
2. Drink non-carbonated water only.
3. Do not smoke.
4. Do not drink alcoholic beverages.
5. One hour before the test – exclude stressful situations and physical activity.
6. One week before the test – cancel the intake of hormonal drugs (if such cancellation is impossible, you should warn your doctor about the amount and dose of drugs taken).

If a blood test for leptin is ordered along with other instrumental examinations, the test should be done before any of them.

Venous blood is taken on an empty stomach and transported to the laboratory at a temperature range of +4 to +8 degrees Celsius for 24 hours and always in an upright position. Samples are stored in special thermoses or containers maintaining a low temperature. Freezing of anticoagulant is not allowed.

The immunofluorescent assay is used for testing, the unified testing method is ELISA. The ELISA test is based on the detection of leptin when a conjugate is added. After a conjugation reaction, the labeled reagent binds only to leptin. The essence of the reaction is a change in color, the intensity of which correlates with the quantitative characteristic of leptin that is detected in plasma.

Normal values

The hormone values in venous blood are affiliated with the gender and age of the patient. On average, the norm for leptin in adults who are not overweight is 2 to 5.6 ng/ml in men and 3.7 to 11.1 ng/ml in women. There are no standards for leptin in plasma according to international standards, the reference values are only laboratory test records, which correlate not only with the method of testing, but also with the reagents used in a particular laboratory. Variations up to 105.0 ng/ml are possible, since the hormone concentration is correlated with body weight. On this basis, the physician must consider the anthropometric data of the patient and his or her gender when evaluating the test result.

Results Assessment

The main reason for the increase in leptin levels in the blood is considered to be overeating, a consequence of which is food obesity. The hormone is correlated primarily with the weight of the patient. A 10% weight gain results in a 300% increase in leptin in the blood.  A 10% weight loss helps reduce hormone concentrations by only 53%. The increase in steroids may be due to leptin resistance associated with pathology of leptin transport by soluble proteins or their receptors. Increased steroids suppress insulin synthesis and force transverse striated muscle and adipose tissue to resist its effects.

Higher concentrations of leptin also provoke thrombosis. Blood clots are formed by direct contact between leptin and receptors on platelets. As a result, the patient’s cardiovascular pathology progresses. Another reason for the increased concentration of leptin in blood may be insulin dependent diabetes mellitus. When the level of the hormone is high, the effect of insulin on hepatocytes is blocked, which activates the growth of sugar levels in type 2 diabetes.

The main reasons for the minimization of hormone levels in the bloodstream are starvation, which causes lack of weight gain and imbalance in the function of receptors responsible for hormonal processes in the body. Chronic inflammatory pathologies such as psoriasis, rheumatism, tuberculosis, as well as cancer, and lack of sleep also help drop leptin levels. In addition, a gene mutation associated with a deficiency in steroid production is considered a trigger for a drop in leptin concentrations in the bloodstream.