Hypophysitis is a rare condition characterized by inflammation of the pituitary gland, which can disrupt its normal function. This inflammation may cause the gland to enlarge, leading to hormone imbalances and various symptoms.
Understanding Hypophysitis
The pituitary gland, also known as the hypophysis, is a small, pea-sized endocrine gland often called the “master gland.” Located at the base of the brain, it produces and releases hormones that control other endocrine glands, such as the thyroid, adrenal glands, and reproductive organs. It is connected to the hypothalamus, which influences hormone production.
The gland has two main parts: the anterior and posterior pituitary. The anterior lobe produces hormones like growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), prolactin, and gonadotropins (FSH, LH). The posterior lobe stores and releases antidiuretic hormone (ADH) and oxytocin, which are produced by the hypothalamus. Hypophysitis interferes with the pituitary’s ability to produce or release these hormones, leading to deficiencies.
Causes and Classifications
Hypophysitis can arise from various factors, leading to its classification into primary and secondary forms. Primary hypophysitis occurs when the inflammation is confined to the pituitary gland without an identifiable external cause, often believed to be an autoimmune disorder. Secondary hypophysitis, conversely, is triggered by an external factor, such as a systemic disease, infection, or certain medications.
The most common primary type is lymphocytic hypophysitis, marked by immune cell infiltration, primarily lymphocytes. It is more common in women, especially during late pregnancy or postpartum, and can link to other autoimmune conditions. Another primary type is granulomatous hypophysitis, identified by immune cell clusters forming granulomas. IgG4-related hypophysitis is a distinct variant with dense IgG4-positive plasma cell infiltrates, often part of a systemic condition.
Beyond autoimmune responses, certain cancer immunotherapies, specifically immune checkpoint inhibitors, are recognized causes of drug-induced secondary hypophysitis. Infections, though less frequent, can also lead to pituitary inflammation. In some instances, the cause remains unknown, classifying it as idiopathic.
Recognizing the Signs
Hypophysitis indicators stem from two main issues: physical enlargement of the inflamed gland and hormonal deficiencies. The expanding gland can pressure nearby structures, especially the optic chiasm, leading to headaches and visual disturbances like blurred or double vision.
Hormonal deficiencies cause a broad range of systemic symptoms. Low adrenocorticotropic hormone (ACTH) can cause fatigue, nausea, vomiting, and low blood pressure. Thyroid-stimulating hormone (TSH) deficiency may lead to unexplained weight changes. Reduced gonadotropins (LH and FSH) can result in irregular or absent menstrual periods in women and decreased libido or erectile dysfunction in men. Antidiuretic hormone (ADH) deficiency can cause excessive urination and thirst.
Diagnosis and Treatment Approaches
Diagnosing hypophysitis involves clinical evaluation, laboratory tests, and imaging studies. Initial assessment includes blood tests to measure various pituitary hormones like ACTH, cortisol, TSH, free T4, LH, FSH, estradiol, testosterone, IGF-1, and prolactin. Low levels in multiple hormone systems raise suspicion.
Magnetic Resonance Imaging (MRI) of the brain is a primary diagnostic tool. MRI can reveal features like pituitary gland enlargement or thickening of the pituitary stalk, indicating inflammation. While a pituitary biopsy offers definitive confirmation by examining tissue, it is generally reserved for uncertain or severe cases due to its invasive nature.
Treatment aims to reduce inflammation and address hormonal deficiencies. Corticosteroids, such as high-dose glucocorticoids, are often first-line to decrease inflammation and alleviate pressure. Hormone replacement therapy is essential for imbalances, with specific hormones like levothyroxine for thyroid deficiency and desmopressin for ADH deficiency. If mass effect symptoms are severe or medical therapy is ineffective, surgery may be considered to relieve pressure.