Pseudoacromegaly is a rare clinical entity characterized by acromegaloid features without growth hormone (GH) excess and with normal insulin-like growth factor 1 (IGF-1) levels. In adults, untreated primary hypothyroidism with pituitary hyperplasia (PH) is the only well-documented endocrine cause. PH may mimic a pituitary adenoma on neuroimaging, potentially leading to unnecessary surgery. We report the case of a 34-year-old woman presenting with progressive weight gain, coarse facial features, acral enlargement, anemia, menstrual irregularities, and symptoms of hypothyroidism. Laboratory evaluation revealed markedly elevated thyroid-stimulating hormone (TSH) (>150 mIU/mL), low free thyroxine (T4L) (0.15 ng/dL), normal IGF-1, and mild hyperprolactinemia. Pituitary magnetic resonance imaging (MRI) demonstrated symmetric enlargement with homogeneous enhancement and suprasellar extension, consistent with PH. A diagnosis of severe untreated primary hypothyroidism with pseudoacromegaly was established, and levothyroxine 150 μg/day was initiated. After 20 weeks, repeat MRI showed complete resolution of pituitary enlargement and clinical features. This case illustrates an uncommon presentation of severe hypothyroidism with combined pseudoacromegaly and PH. The pathophysiology involves chronic thyrotropin-releasing hormone (TRH) stimulation of thyrotrophs and lactotrophs, leading to pituitary enlargement and soft tissue changes due to glycosaminoglycan deposition. Recognition of this association is crucial, as thyroid hormone replacement can reverse both PH and acromegaloid features, avoiding unnecessary neurosurgical intervention. In patients presenting with acromegaloid features and pituitary enlargement, primary hypothyroidism should be considered. Prompt diagnosis and levothyroxine therapy can lead to complete clinical and radiological resolution.