Prolactin Disorders

Causes of high prolactin levels in the blood

Primary Hypothyroidism: this is due to increased TRH levels which is known to stimulate prolactin levels

Renal failure: prolactin is mainly excreted from the body from the kidneys. Reduced kidney function can lead to higher levels of prolactin.

Medications: there are a long list of these that can potentially cause high prolactin levels including those below. Usually medication induced high prolactin elevations are in the 20-100 mg/L range but metoclopramide, phenothiazines, and risperdone can lead to levels exceeding 200mg/dl

Pituitary stalk interruption: This is either due to a pituitary tumor or other brain tumor in the area of the pituitary which leads to higher levels of prolactin secretion due to interruption of the natural inhibition of prolactin secretion . Your Houston endocrinologist can explain this in great detail. Prolactinoma is the most common pituitary tumor that over secretes the hormone prolactin.

Idiopathic: This is when no obvious cause is seen and is most commonly due to a pituitary tumor that is too small to see on MRI.

Physiologic: Coitus, exercise, lactation, sleep, pregnancy, stress, any chest wall stimulation

Symptoms of a Prolactinoma

Men

Usually these tumors are large at time of diagnosis (macroprolactinoma) and cause hypogonadotropic hypogonadism as well as cranial nerve deficits which include vision changes. The symptoms of this are not always obvious to men. The symptoms would include reduced libido, gynecomastia (enlargenment of the breast tissue), erectile dysfunction, and rarely infertility.

Women

The symptoms of prolactinomas in women depend on their age and size of tumor. The large masses present with cranial nerve deficits which include vision changes. In premenopausal women hypogonadotropic hypogonadism can result in irregular or missed menstrual cycles (amenorrhea) as the first sign even in very small prolactinomas (microprolactinoma). High prolactin levels can cause galactorrhea (breast milk production) in non-lactating women. Postmenopausal women may have no symptoms until the tumor is large.

Treatment goals

The treatment of prolactinoma usually does not require surgery. Many of these tumors respond very well to hormonal medications called dopamine agonists which are prescribed by the endocrinologists at Houston Thyroid and Endocrine.

1.Reduction of prolactin concentrations and its clinical consequences, such as gonadal dysfunction, infertility, and osteoporosis

2.Reduction of tumor mass, thereby relieving visual field defects and hypopituitarism

3.Preservation of residual pituitary function

4.Prevention of continuing growth of tumor mass

5.Improvement of quality of life.

Some indications for surgical treatment

In some patients medical treatment does not result in adequate control of micro- and macroprolactinomas. These indications include but are not limited to intolerance to dopamine agonists medications, resistance to the effects of dopamine agonists, impending vision loss due to large size of the prolactinoma.

The surgery to remove these tumors usually a transsphenoidal surgery. The success rates for surgery between microprolactinomas and macroprolactinomas are different. Surgical success rates are highly dependent upon the experience of the neurosurgeon. Surgery restores prolactin concentrations to normal more often in microprolactionomas than in macroprolactinomas. One of the rare complications of this type of surgery include hypopituitarism which is a loss of all the hormones produced by the pitiutary.

Summary

When a mild prolactin elevation is found, physiologic, pathologic, iatrogenic, and other endocrine causes need to be excluded before making the diagnosis of a small prolactin-secreting tumor since MRI of the pituitary can sometimes have incidental pituitary lesions. Very high prolactin levels in are almost always indicative of a prolactin-secreting tumor called prolactinomas, except during pregnancy. Elevated prolactin levels cause galactorrhea and suppress the hypothalamic-pituitary-gonadal axis, which results in hypogonadism and a progressive decrease in the bone mineral density. Untreated prolactin-secreting tumors usually grow slowly but there are exceptions. Treatment with dopamine agonists are usually well tolerated and quickly effective in normalizing the prolactin level and shrinking the tumor mass of even large prolactin-secreting tumors. Speak to the endocrinologists at Houston Thyroid and Endocrine Specialists for up to date treatment options.