At my practice in Austin, Texas when we are looking at the endocrine system I am often asked if and how the pituitary gland is related to the thyroid gland? They are hugely related. What many people may not know is that the thyroid stimulating hormone (TSH) is actually made in the pituitary gland and sent down to the thyroid to ‘stimulate’ the thyroid to make hormones. When an endocrinologist runs the TSH, they are not only checking thyroid function, but also pituitary function.
The Pituitary Gland has two parts – The anterior and posterior. The posterior pituitary does not produce its own hormones, but only stores and releases the hormones created by the hypothalamus. The two posterior pituitary hormones are oxytocin and an antidiuretic hormone. These hormones travel from the hypothalamus to the posterior pituitary and are stored there until they are released in response to nerve impulses. oxytocin is used to regulate milk secretion and contractions of uterus during birthing; and the antidiuretic hormone helps regulate kidney
The anterior pituitary produces and secretes its own hormones and then releases them into the bloodstream when signaled. The anterior pituitary gland produces and stores the following hormones:
Adrenocorticotropic hormone – which stimulates the adrenal glands to secrete steroid hormones, principally cortisol. It also produces the growth hormone which regulates growth, metabolism and body composition.
The luteinizing hormone and follicle stimulating hormone – They are known as known as gonadotrophins. They act on the ovaries or testes to stimulate sex hormone production and egg and sperm maturity.
Another important hormones produces here in the anterior pituitary gland is prolactin, which stimulates milk production
The last and most common hormone made in the anterior pituitary is the thyroid stimulating hormone (TSH).
The TSH stimulates the thyroid gland to secrete the thyroid hormone thyroxine. Thyroxine (T4) and triiodothyronine (T3) are the primary circulating thyroid hormones. The thyroid produces T4 in significantly greater quantities (in a ratio of 17:1) than T3. T3 is actually the active form, and is the one responsible for energy and metabolism. T4 must be converted into the more active thyroid hormone T3 by removing one iodine atom from the T4. Selenium and vitamin E are needed to make this conversion. So when looking at an imbalanced thyroid you often have to start by looking up stream to make sure the pituitary is doing its job.