The pituitary gland is a small endocrine gland that is instrumental in regulating a wide range of bodily functions. Its influence extends throughout the body, earning it the description of the “master gland” for its role in directing other hormone-secreting glands. This gland’s activity affects processes ranging from growth and metabolism to stress responses and reproduction.
Anatomy and Location of the Pituitary Gland
The pituitary gland is a small, pea-sized structure, weighing around 0.5 grams in adults. It is located at the base of the brain within a bony depression in the sphenoid bone called the sella turcica. This protective enclosure situates the gland behind the bridge of the nose. The gland is physically and functionally connected to the hypothalamus, which controls its function, via a structure known as the pituitary stalk or infundibulum.
This connection is a bridge between the nervous system and the endocrine system. The gland is composed of two distinct parts: the anterior pituitary and the posterior pituitary. These lobes have different origins and are responsible for producing and releasing different hormones. The anterior lobe makes up about 80% of the gland and is composed of glandular tissue, while the posterior lobe is an extension of nervous tissue from the hypothalamus.
Hormones Produced by the Pituitary Gland
The two lobes of the pituitary gland secrete different hormones that act on various target organs. The anterior lobe produces a range of hormones that regulate several physiological processes. One of these is Growth Hormone (GH), which stimulates growth in children and helps maintain body structure in adults. Thyroid-Stimulating Hormone (TSH) travels to the thyroid gland to prompt the release of thyroid hormones, which control metabolism.
The anterior lobe also secretes Adrenocorticotropic Hormone (ACTH), which stimulates the adrenal glands to produce cortisol, a hormone for stress response and blood pressure. For reproduction, it produces Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH). In women, these hormones act on the ovaries to regulate the menstrual cycle; in men, they act on the testes to promote sperm production. Prolactin, another hormone from this lobe, stimulates milk production after childbirth.
The posterior pituitary, in contrast, does not synthesize its own hormones but stores and releases two hormones produced in the hypothalamus. Antidiuretic Hormone (ADH), also known as vasopressin, acts on the kidneys to regulate water balance and blood pressure. Oxytocin is the other hormone, which stimulates uterine contractions during childbirth and promotes the release of milk during breastfeeding.
Historical Use of Cadaver-Derived Pituitary Glands
Before modern biotechnology, the only source of human growth hormone (hGH) for medical use was from the pituitary glands of human cadavers. Beginning in the late 1950s, a process was developed to extract hGH from thousands of these glands collected after death. This cadaver-derived hormone was a treatment for children with severe growth deficiencies, a condition that could lead to pituitary dwarfism.
For these children, the treatment allowed for more typical growth and development. Animal-derived growth hormone had proven ineffective because the molecular structure was too different from the human version to work in the body. For several decades, from 1959 to 1985, this was the only available therapy, despite logistical challenges and limited supply.
The Shift to Synthetic Hormone Treatments
The practice of using cadaver-derived hGH came to a halt in 1985. It was discovered that some batches of the hormone were contaminated with infectious proteins called prions, which caused a fatal neurodegenerative condition called Creutzfeldt-Jakob disease (CJD). The long incubation period of the disease meant that individuals could receive the contaminated hormone in childhood and not show symptoms for many years. This discovery created a need for a safer alternative.
The solution came from genetic engineering. Scientists developed a method using recombinant DNA technology to produce a synthetic version of human growth hormone. This process involves inserting the human gene for growth hormone into bacteria, which then produce the hormone in large quantities. This synthetic hormone, known as somatropin, is identical to the one produced by the human body but carries no risk of prion contamination. Today, recombinant hGH is the standard of care for treating growth hormone deficiency, replacing the use of glands from human sources.