The pituitary gland (hypophysis) is a small endocrine gland located at the base of the brain in the sella turcica. It is connected to the hypothalamus via the pituitary stalk (infundibulum) and is divided into two main parts:
- Anterior Pituitary (Adenohypophysis)
- Posterior Pituitary (Neurohypophysis)
Anterior Pituitary (Adenohypophysis)
- Origin
- Derived from oral ectoderm (Rathke’s pouch).
- Consists of glandular epithelial cells that synthesize and secrete several key hormones.
Major Hormones Secreted
| Hormone | Full Name | Main Function | Cell Type |
|---|---|---|---|
| FSH | Follicle-Stimulating Hormone | Stimulates gametogenesis (spermatogenesis in males, follicular growth in females) | Basophil |
| LH | Luteinizing Hormone | Stimulates testosterone secretion in males, ovulation, and corpus luteum formation in females | Basophil |
| ACTH | Adrenocorticotropic Hormone | Stimulates cortisol production from the adrenal cortex | Basophil |
| TSH | Thyroid-Stimulating Hormone | Stimulates thyroid hormone synthesis and release | Basophil |
| Prolactin (PRL) | — | Stimulates milk production | Acidophil |
| GH (Somatotropin) | Growth Hormone | Promotes growth, protein synthesis, and lipolysis | Acidophil |
| β-Endorphin | — | Acts as an endogenous opioid peptide | Basophil |
| MSH (Melanocyte-Stimulating Hormone) | — | Regulates skin pigmentation (from the intermediate lobe) | — |
Hormone Subunits
- α-subunit: Common to TSH, LH, FSH, and hCG
- β-subunit: Determines hormone specificity
POMC Derivatives
The proopiomelanocortin (POMC) precursor is cleaved to form:
- ACTH
- β-Endorphin
- MSH (Melanocyte-Stimulating Hormone)
Posterior Pituitary (Neurohypophysis)
Origin
- Derived from neuroectoderm (extension of hypothalamic tissue).
Function
- Stores and releases, but does not synthesize, the following hormones made in the hypothalamus:
- ADH (Vasopressin) – Synthesized in the supraoptic nucleus
- Oxytocin – Synthesized in the paraventricular nucleus
These hormones are transported to the posterior pituitary via neurophysins (carrier proteins).
Summary Table
| Region | Embryologic Origin | Major Hormones | Produced by | Released by |
|---|---|---|---|---|
| Anterior Pituitary | Oral ectoderm (Rathke pouch) | FSH, LH, ACTH, TSH, PRL, GH, β-Endorphin | Pituitary cells | Pituitary cells |
| Posterior Pituitary | Neuroectoderm | ADH, Oxytocin | Hypothalamic nuclei | Posterior pituitary neurons |
Key Points to Remember
- Anterior pituitary = Glandular tissue → synthesizes hormones.
- Posterior pituitary = Neural tissue → stores and releases hypothalamic hormones.
- α-subunit is shared among TSH, LH, FSH, and hCG.
- POMC gives rise to ACTH, β-Endorphin, and MSH.
- B-FLAT and Acid PiG help recall hormone cell types.
Learning Objective
By the end of this topic, you should be able to:
- Describe the anatomy and embryologic origin of the pituitary gland.
- List the hormones secreted by the anterior and posterior pituitary.
- Identify the cell types and hormone subunits involved.
- Explain the relationship between the hypothalamus and pituitary in hormone regulation.
Activity:
