A tumor in your pituitary gland can disrupt hormones throughout the body. Weight loss after pituitary tumor surgery can be the natural result of hormones finding balance again.

Pituitary tumors are abnormal bundles of cells that grow in the pituitary gland.

The pituitary gland is located at the base of your brain in a bony notch above the soft palate of your mouth. It’s made of two parts — the anterior and posterior pituitary — both of which are responsible for the production, storage, or release of hormones necessary throughout the body.

Almost all pituitary tumors are adenomas, a noncancerous type of tumor also referred to as a pituitary neuroendocrine tumor.

When a tumor develops in the pituitary gland, excess hormones can generate a variety of symptoms, including weight gain. For this reason, weight loss after pituitary tumor surgery is often anticipated as hormones reregulate.

The pituitary gland secretes hormones that help regulate body weight. When you develop a functional pituitary tumor, excess hormones can cause weight fluctuations.

Corticotroph adenomas, for example, are pituitary tumors that make extra adrenocorticotropic hormone (ACTH). Too much ACTH cues the body to produce an excess of cortisol, which can cause:

Weight gain is just one side of the coin, however. You can also experience weight loss, depending on the hormones affected by a pituitary tumor.

Thyrotroph adenomas, for example, are rare pituitary tumors that produce thyroid-stimulating hormone (TSH). The TSH causes the thyroid gland to produce excess amounts of thyroid hormones, leading to a condition called hyperthyroidism.

Hyperthyroidism naturally increases your metabolic rate. Even with a ravenous appetite, it can mean unintentional weight loss.

Weight loss after pituitary tumor surgery is possible but not necessarily predictable.

Removing tumors that directly influence weight gain, like corticotroph adenomas, can reduce the hormones promoting excess body weight. As those hormones decrease, it’s natural to see some weight loss.

Weight loss after pituitary tumor surgery is always a possibility, regardless of tumor type.

The pituitary gland’s regulatory action on your body weight involves multiple hormones, and any surgery can cause unavoidable injury to pituitary tissue that temporarily affects hormone production.

While your doctor can prescribe medications to replace missing hormones, weight loss — and weight gain — are possible side effects, depending on the hormones affected.

Other factors, like co-existing conditions, can also affect how and if your weight changes after surgery.

A 2022 study looking at postsurgery weight changes among people who had somatotroph pituitary adenomas (tumors located on the anterior pituitary gland) removed found weight loss and weight gain were both reported.

However, people also living with diabetes mellitus were more likely to experience weight gain rather than weight loss.

Pituitary tumor surgery is the first-line treatment option for most pituitary tumors that are causing health challenges.

Your surgeon will decide on either a transsphenoidal procedure, which goes through the nasal passages to reach the pituitary gland, or a craniotomy, a more complicated, front-skull approach used for large and complex tumors.

Your recovery will vary based on the procedure, the type of tumor removed, and if any surrounding tissues were involved. Most people can go home after 2 or 3 days in the hospital.

In the days to weeks after the procedure, your healthcare team will routinely measure hormone levels in your blood to ensure the pituitary gland is functioning as it should.

Diagnostic imaging done through MRI scans is also a part of follow-up care. Doctors closely watch the tumor site and surrounding structures, not just for tumor regrowth, but to ensure no postsurgical complications, like meningitis, have occurred.

Due to the proximity of the pituitary gland to the ocular nerves, your postsurgical routine may involve regular visits to an eye specialist.

Transsphenoidal surgery is the most routine pituitary tumor surgery performed. It’s considered minimally invasive with few side effects.

Most people can expect to experience a headache and congestion up to 2 weeks after the procedure.

Other possible side effects of pituitary tumor surgery include:

A small 2020 study on postoperative pituitary tumor surgery complications found that infection was the most common complication, followed by low hormone production, CSF leakage, diabetes insipidus, and electrolyte imbalance.

Pituitary tumors can cause excess hormone production that affects the regulation of your body weight. Too much of one hormone may promote weight gain, while too much of another may encourage weight loss.

Having a pituitary tumor removed can also alter your weight. As extra hormone production subsides and pituitary tissue recovers, you may notice weight gain or weight loss after pituitary tumor surgery.

Pre-existing conditions, like diabetes, may play a role in how weight changes after pituitary tumor surgery.