Key Clinical Message:In cases of pituitary lesions with elevated TSH, a comprehensive diagnostic approach that includes biochemical, clinical, and radiological assessment is essential. Not all pituitary masses are adenomas. Pituitary hyperplasia secondary to primary hypothyroidism can mimic adenomas, particularly prolactinomas, due to associated hyperprolactinemia. Thyroxine replacement therapy often reduces pituitary hyperplasia, making hormonal profiling essential to avoid unnecessary surgical interventions. Patient compliance with hormone therapy is also a key factor, as non-compliance can lead to persistent symptoms and impact outcomes. Early specialist involvement and a multidisciplinary approach are beneficial in these complex cases to ensure accurate diagnosis and timely intervention.Introduction :The pituitary gland, often called the ”master gland” of the body, regulates numerous essential functions by releasing various hormones. Structurally, the gland is divided into an anterior and a posterior lobe. The anterior lobe produces several vital hormones, including human growth hormone (HGH or GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin. The posterior lobe produces oxytocin and antidiuretic hormone (ADH). The hypothalamus controls all these hormones, which regulate their release through specific signaling chemicals.Pituitary adenomas, or benign tumors of the pituitary gland, can be classified by size—macroadenomas are more significant than 10 mm, while microadenomas are smaller. They are also categorized as either secreting or non-secreting, depending on whether they actively release hormones. The most common secreting adenoma is prolactinoma, which overproduces prolactin (1). Pituitary hyperplasia, on the other hand, involves the overgrowth of pituitary cells and may affect either specific hormone-producing cells or the entire gland. Both adenomas and hyperplasia can present as a pituitary mass on imaging, which can complicate diagnosis.In primary hypothyroidism, inadequate thyroid hormone production can result in elevated TSH levels and pituitary hyperplasia due to loss of negative feedback in the hypothalamic-pituitary-thyroid axis. Studies indicate that 25-81% of hypothyroid patients present with pituitary hyperplasia (2). Additionally, thyroid-stimulating hormone (TSH)-secreting adenomas, or TSHomas, are rare, accounting for only 0.5% to 3% of all pituitary tumors (3). These tumors are typically characterized by elevated levels of free thyroid hormones (FT4 and FT3) in the presence of non-suppressed TSH, often presenting clinically with symptoms of hyperthyroidism (4). Differentiating between TSHomas, thyroid hormone resistance, and other causes of elevated TSH can be challenging.This case series presents three patients with elevated TSH and pituitary lesions, each with a unique clinical outcome and treatment pathway. Although their initial symptoms were similar varying diagnoses led to distinct management strategies. This series highlights the diverse presentations of pituitary lesions with elevated TSH and underscores the importance of systematic evaluation to avoid misdiagnosis and unnecessary surgical interventions.
