Pituitary Gland
Endoscopic Pituitary Surgery
What is pituitary gland?
The pituitary
gland is a small gland found at the base of the brain
just below the hypothalamus, to which it is attached via nerve fibers (Fig.1.1). It produces many hormones that travel throughout the body and directly affect the body function and also indirectly by controlling other endocrine glands in the body.
What is function of pituitary gland?
Pituitary gland has 2 lobes, the anterior, or front, and the posterior, or back. Each lobe is responsible for releasing specific hormones. The following hormones are made in the anterior (front part) of the pituitary gland(Fig.1.2):
Fig 1.2
- Prolactin - Prolactin stimulates breast milk production after childbirth. It also affects sex hormone levels from ovaries in women and from testes (testicles) in men, as well as fertility.
- Growth hormone (GH) - GH stimulates growth in childhood and is important for maintaining a healthy body composition and well being in adults. In adults, GH is important for maintaining muscle mass and bone mass. It also affects fat distribution in the body.
- Adrenocorticotropic hormone (ACTH) - ACTH stimulates the production of cortisol by the adrenal glands-small glands that sit on top of the kidneys. It helps maintain blood pressure and blood glucose levels, and is produced in larger amounts when we’re under stress-especially after illness or injury.
- Thyroid-stimulating hormone (TSH) - TSH stimulates the thyroid gland to produce thyroid hormones, which regulate the body's metabolism, energy balance, growth, and nervous system activity.
- Luteinizing hormone (LH) - LH stimulates testosterone production in men and egg release (ovulation) in women.
- Follicle-stimulating hormone (FSH) - FSH promotes sperm production in men and stimulates the ovaries to produce oestrogen and develop eggs in women.
- The following hormones are stored in the posterior (back part) of the pituitary gland:
- Antidiuretic hormone (ADH) - ADH, also called vasopressin, conserves body water by reducing the amount of water lost in urine. Underproduction of ADH results in a disorder called diabetes insipidus characterized by inability to concentrate the urine and, consequently, excess urination leading potentially to dehydration.
- Oxytocin – Oxytocin causes milk to flow from the breasts in breastfeeding women, and may also help labor to progress.
What type of tumours develop in pituitary gland? What are the problems do these tumours cause?
- The most frequent type of pituitary disorder is a pituitary gland tumour. These tumours are fairly common in adults. They are almost always benign (not cancer).
- There are two types of tumours—secretory and non-secretory. Secretory tumours produce too much of a hormone normally made by the pituitary, and non-secretory tumours do not. Both types of tumours can cause problems if they are large and interfere with normal function of the pituitary gland and/or nearby structures in the brain.
- The problems caused by pituitary tumours fall into three general categories:
- Hypersecretion: Too much of any hormone in the body is caused by a secretory pituitary tumour. Examples include acromegaly, Cushing's disease and prolactinoma.
- Hyposecretion: Too little of any hormone in the body can be caused by a large pituitary tumour, which interferes with the pituitary gland’s ability to produce hormones. Hyposecretion can also result from surgery or radiation of a tumour.
- Tumour mass effects: As a pituitary tumour grows and presses against the pituitary gland or other areas in the brain, it may cause headaches, or push upwards and interfere with vision – a visual field defect. Very occasionally, the tumour may expand sideways and cause double vision as it affects the nerves, which control eye movements.
- Injuries, certain medications, bleeding inside or close to the pituitary, and other conditions can also affect the pituitary gland. Loss of normal pituitary function also can occur after major head trauma.
How is pituitary tumour diagnosed?
When a pituitary tumour is suspected, a physician will perform a physical examination and vision testing to detect loss of peripheral vision. Hormone testing of the blood and urine and MRI of the brain are used to confirm diagnosis.
What is the treatment for pituitary tumours?
Early intervention provides the best chance for cure or control of a pituitary tumour and its side effects. There are three types of treatment used for pituitary tumours: surgical removal of the tumour, radiation therapy to destroy tumour cells and medication therapy to shrink or eradicate the tumour. Hormone replacement therapy may also be required.
For prolactinoma, treatment of choice is medical therapy. With medical management, about 80 percent of patients have prolactin levels restored to normal. If the tumours do not respond to medication therapy, then surgery is considered.
For all other tumours, surgical removal is the treatment of choice. For residual or recurrent tumours and when the patient is not fit for surgery, radiotherapy and/or medical treatment is considered.
What are the goals of pituitary adenoma surgery?
- Complete tumour removal
- Preservation of gland function
- Restoration of vision
Fig 1.3
Which is the currently favoured surgical technique?
The pituitary gland lies in the roof of sphenoid sinus in an area called sella turcica. it is surrounded on either side by the internal carotid arteries (which takes blood to brain) and above by the optic chasm and brain.
Most of these tumours are approached through the nasal cavity and sphenoid sinus. It is known as transsphenoidal approach. Microscope was used earlier for this surgery. Currently, building on the experience in endoscopic sinus surgery, otolaryngologists accumulated considerable expertise in pituitary tumour resection
aided by endoscopic techniques (Fig.1.3). The endoscope enables a panaromic view of the sella with excellent magnification and illumination superior to the operative microscope (Fig.1.4). Angled scopes allow the surgeon to view the hidden areas (lateral parasellar and suprasellar areas) which was not possible with the microscope. The improved visualization possible with the endoscope reduces carotid and hypothalamic injury and makes it possible to remove the tumour completely. Computer assisted surgical navigation system is used where the pneumatization of sphenoid is of pre-sellar / conchal type. Currently, transnasal endoscopic transsphenoidal surgery is the preferred surgical technique.
Fig 1.4 Picture shows narrow field of vision with microscope and the panaromic wide field of vision with telescope
The transcranial approach, or craniotomy, is less commonly used and reserved for particularly large and invasive tumours which cannot be safely removed through the transsphenoidal route.
What are the safety measures taken during endoscopic surgery?
Most of the pituitary adenomas (>95%) are removed via the nose using endoscopic endonasal technique. At Apollo Cancer Centre, we aim at maximizing tumour removal and minimizing complications through experience and use of the best use of technology including high-definition endoscopy, intraoperative navigation and the endoscopic Doppler probe for blood vessel localization (Fig.1.5).
Our experience in Endoscopic Pituitary Surgery
From January 1997 to December 2020, our team at the Apollo Cancer Centre, Chennai has carried out 1245 endoscopic pituitary surgeries successfully. Out of 1245 sellar lesions we managed, 96% of them are pituitary adenomas. Other conditions treated were craniopharyngiomas (2%), meningiomas (0.2%), Rathke’s cleft cysts (0.4%), inflammatory lesions (0.6%) and malignant tumours (0.16%). Youngest patient we have operated so far was 8 years old and the age of the patient need not be a limiting factor.
Conclusion:
Surgery for pituitary lesions has become greatly refined from the time Cushing described transsphenoidal approach. Endoscopic transsphenoidal pituitary surgery is now a proven and safe method of removing pituitary lesions and has been embraced as the preferred technique the world over.
The Heart Of Clinic
Dr. C. Rayappa MBBS, DLO, FRCS(Edin)
SENIOR CONSULTANT
+91 44 3315 1105
Dr. C. Rayappa graduated from Madras Medical College, Chennai, India in 1982. He completed his post graduation in Otolaryngology (ENT)
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The Heart Of Clinic
Dr. C. Rayappa MBBS, DLO, FRCS(Edin)
SENIOR CONSULTANT
+91 44 3315 1105
Dr. C. Rayappa graduated from Madras Medical College, Chennai, India in 1982. He completed his post graduation in Otolaryngology (ENT)