The endocrine system functions to ensure that all hormones are secreted at the right time and a precise concentration in response to various stimuli. Endocrine glands are found throughout the body, with the main glands being:
- pineal gland
- pituitary gland
- ovaries, testes
- thyroid gland
- parathyroid gland,
- adrenal glands
The hormones released from these glands differ in function depending on their tissue type and location. For example, the adrenal glands release the fight-or-flight hormone, adrenalin. The pancreas releases insulin to reduce sugar levels after a meal, and the thyroid gland releases thyroid hormones which are responsible for regulating metabolism.
Research has found that single nucleotide polymorphisms (SNPs) in the genes which encode these hormones, or other closely related proteins, affect the correct functioning of the hormones, leading to the development of several pathologies.
Diabetes mellitus refers to a group of diseases in which blood sugar levels are higher than normal. This could either be because your pancreas fails to produce insulin to ensure efficient uptake of glucose into your cells (Type I diabetes), or the cells in your body fail to respond effectively to insulin (Type II diabetes).
Adipose (fat) tissue
Research has shown that SNPs in genes associated with the fat tissue in the body have a strong correlation with the development of Type II diabetes. Adiponectin is a protein hormone secreted by fat tissue and is a well-known regulator of glucose levels, fat metabolism, and insulin sensitivity 1. Several population-based studies have reported an association between SNPs in the adiponectin gene and circulating levels of adiponectin. The studies show that low circulating levels of adiponectin were reported to be associated with insulin resistance, Type II diabetes mellitus, and central obesity2.
Adrenal Gland Hormones
The adrenal gland is positioned to sit on top of each of the kidneys and is responsible for the secretion of the following hormones:
These hormones play essential roles in ensuring the normal functioning of various body process which include, but are not limited to:
- Balancing of sex hormones, including estrogen and testosterone
- Blood sugar levels
- Blood pressure
- Electrolyte and water balance
- Sexual development before and during puberty
- Stress response
Although cortisol is secreted by your adrenal glands, its secretion is controlled by the hypothalamus and the pituitary gland in the brain. Its main function is to allow the body to respond to stress, increase the body’s metabolism of glucose, control blood pressure and, reduce inflammation.
Cholesterol is important to produce cortisol and therefore any dysregulation in the synthesis of cholesterol will affect the production of cortisol. Research has found that SNPs in the gene coding for the protein that is responsible for the final step of cholesterol synthesis are associated with a disorder known as Smith-Lemli-Opitz syndrome 3. This is a metabolic disorder characterized by very low cholesterol, accompanied by varying levels of congenital malformations, and represents the worst-case scenario. This gene is also associated with being vital in the switch between cholesterol and vitamin D synthesis.
Thyroid hormones play key roles in metabolic and developmental processes in the body. Most of these effects are mediated by the active thyroid hormone T3. These include:
- Brain development
- Skeletal maturation
- Heat production
- Oxygen consumption
- Contractility of the heart
Thyroid Hormone Receptor
The growth and function of the thyroid gland are controlled by thyroid-stimulating hormone through its receptor 4. Research has found that SNPs in genes coding for this receptor have been identified as causes of thyroid diseases. One study found that a particular SNP was correlated with low circulating levels of thyroid hormone and in some cases resulted in hypothyroidism 5.
It is noteworthy that small changes in gene sequences have hormonal effects that may lead to pathogenic conditions. Therefore, Identifying pathogenic SNPs within an individual’s genes that encode various endocrine hormones may therefore be informative, and drive a tailored nutrition or lifestyle change that can support hormonal processes to encourage optimal health and wellbeing.