Pituitary Gland

What is the pituitary gland?

The pituitary gland (Hypophysis) is a gland located at the base of the skull in a bony cavity called the sella turcica (Turkish saddle). The pituitary itself is small (1 cm) and is divided into two parts or lobes:

Anterior lobe (adenohypophysis)
Posterior lobe (neurohypophysis)

These lobes have different origins; the anterior lobe originates from pharyngeal cells, while the posterior lobe originates from the neural tissue of the hypothalamus.

Which hormones does the pituitary gland secrete?

The pituitary gland secretes more than eight hormones, six of which are secreted by the anterior lobe:

Growth hormone (GH), secreted by somatotropic cells, responsible for growth, cell division, and differentiation.
Thyroid-stimulating hormone (TSH), secreted by thyrotropic cells, stimulates the thyroid gland.
Luteinizing hormone (LH), secreted by gonadotropic cells, responsible for the function of female and male gonads (hormone production).
Prolactin (PRL), secreted by mammotropic cells, initiates the development of mammary glands and milk production.
Follicle-stimulating hormone (FSH), secreted by gonadotropic cells, responsible for the function of female and male gonads (production of sex cells).
Adrenocorticotropic hormone (ACTH), secreted by corticotropic cells, responsible for corticosteroid production.

The hormones secreted by the posterior lobe include:

Vasopressin (antidiuretic hormone, regulates urination).
Oxytocin (primarily involved in childbirth, lactation, and uterine contractions).

Most hormones produced by the pituitary gland are protein or peptide in nature and act on target tissues in the body.

The Pituitary-Hypothalamus Connection

The activity of the anterior pituitary lobe is controlled by the hypothalamus through a feedback mechanism. The hypothalamus secretes releasing/inhibitory factors or hormones that are small peptides (neuropeptides) by structure. It mostly operates through a negative feedback mechanism. These feedback mechanisms allow for balance, i.e., maintaining the body’s homeostasis. All changes the body is exposed to (external and internal factors) are stabilized in this way.
For a long time, the pituitary was considered the main gland in the endocrine system due to the number of hormones it secretes and its significant influence on the entire body. However, after the discovery that pituitary activity is controlled by the hypothalamus, it became clear that the pituitary-hypothalamus connection plays a critical role in various body functions. Many pathological conditions are the result of pituitary dysfunction.

What is hypopituitarism?

When the pituitary gland does not produce enough of one or more hormones, this condition is called hypopituitarism, or reduced pituitary function. The causes can vary, and symptoms depend on which hormone is deficient: