Should cabergoline (cabergoline) be initiated in a patient with mildly elevated prolactin levels, a 2mm pituitary microadenoma, and symptoms suggestive of secondary hypothyroidism, including sweating, despite normal thyroid-stimulating hormone (TSH) levels and corrected hypothyroidism (hypothyroidism)?

From the Guidelines

Cabergoline should be initiated in a patient with mildly elevated prolactin levels, a 2mm pituitary microadenoma, and symptoms suggestive of secondary hypothyroidism.

Rationale

• The patient's symptoms and mildly elevated prolactin levels suggest a prolactinoma, which is typically treated with dopamine agonists like cabergoline 1.
• Cabergoline is the dopamine agonist of choice due to its superior effectiveness and lower adverse effect profile compared to other options like bromocriptine 1.
• The presence of a 2mm pituitary microadenoma also supports the use of cabergoline, as it can help reduce tumor size and normalize prolactin levels 1.
• Although the patient has symptoms suggestive of secondary hypothyroidism, their TSH levels are normal, and they have corrected hypothyroidism, which does not necessarily preclude the use of cabergoline 1.
• The guidelines recommend offering cabergoline as first-line therapy for patients with prolactinoma, even in the presence of visual disturbance or pituitary apoplexy, while carefully monitoring for any deterioration in vision, pituitary function, or general status 1.

Key Considerations

• The patient should be monitored closely for adverse effects, such as gastrointestinal intolerance, postural hypotension, and psychological intolerance, which can be mitigated with small nocturnal dose increments of cabergoline 1.
• The initial dose of cabergoline can be gradually increased up to 3.5 mg per week or even 7 mg per week in exceptional cases, if necessary 1.
• If the patient's prolactin levels are normalized for at least 2 years on medical therapy and there is no visible residual prolactinoma on MRI, a gradual cabergoline dose reduction can be considered to maintain normoprolactinaemia and eventual treatment discontinuation 1.

From the FDA Drug Label

Cabergoline tablets are indicated for the treatment of hyperprolactinemic disorders, either idiopathic or due to pituitary adenomas.

The patient has mildly elevated prolactin levels and a 2mm pituitary microadenoma, which suggests a hyperprolactinemic disorder. Cabergoline can be considered for initiation in this patient, as it is indicated for the treatment of hyperprolactinemic disorders. However, the presence of symptoms suggestive of secondary hypothyroidism, despite normal TSH levels and corrected hypothyroidism, should be carefully evaluated and monitored during treatment with cabergoline 2.

From the Research

Patient Considerations

• The patient has mildly elevated prolactin levels, a 2mm pituitary microadenoma, and symptoms suggestive of secondary hypothyroidism, including sweating, despite normal thyroid-stimulating hormone (TSH) levels and corrected hypothyroidism.
• The decision to initiate cabergoline therapy should be based on the potential benefits and risks of treatment.

Cabergoline Efficacy

• Studies have shown that cabergoline is effective in normalizing prolactin levels and reducing tumor size in patients with prolactin-secreting pituitary adenomas 3, 4.
• A study of 17 patients with prolactin-secreting pituitary adenomas found that cabergoline therapy normalized serum prolactin concentrations in 13 patients (76.5%) and reduced tumor size in 2 patients with macroprolactinomas 3.
• Another study of 151 patients with prolactin-secreting pituitary adenomas found that cabergoline therapy was associated with tumor shrinkage in 102 patients (67.5%) and that lower prolactin levels during treatment were associated with a greater chance of tumor shrinkage 4.

Potential Risks and Considerations

• While cabergoline is generally well-tolerated, it can cause side effects such as dizziness, nausea, and headache 3, 5.
• A study of 14 patients with acromegaly found that cabergoline therapy was associated with side effects that limited therapy in 3 patients (21%) 5.
• The patient's symptoms of secondary hypothyroidism, including sweating, despite normal TSH levels and corrected hypothyroidism, should be carefully monitored during cabergoline therapy.

Diagnostic Considerations

• The coexistence of primary hypothyroidism and TSH-stimulating pituitary macroadenoma can be a rare occurrence and can make diagnosis very challenging 6.
• A high index of suspicion should prompt clinicians to further investigate cases of primary hypothyroidism that do not respond to treatment, including testing for thyroid assay interferences, heterophile antibodies, and anterior pituitary profile 6.