Reactive pituitary hyperplasia can develop as a pituitary (pseudo) macroadenoma in the case of primary hypothyroidism. Hypothyroidism-induced pituitary hyperplasia (PHPH) can be managed medically. Surgery should not be performed if this condition is misdiagnosed as an adenoma. Primary hypothyroidism is a well-known cause of children's slow linear growth. Anterior pituitary enlargement is a rare symptom of severe or long-term illness (pituitary pseudotumor). Thyroid-stimulating hormone-secreting adenomas (TSHomas) are the rarest type of pituitary adenomas, with most endocrinologists seeing just a few cases throughout their lives. In most situations, the diagnosis is difficult, and patients may be referred after presenting with a condition of excessive thyroid-stimulating hormone secretion or a pituitary tumor.In this case study, we describe a 3.5-year-old girl who was referred to our hospital for a surgical assessment of a suspected pituitary neoplastic lesion. It was later determined that the suspected lesion was really pituitary hyperplasia brought on by primary hypothyroidism. Levothyroxine was started, and the dose was increased. The patient was advised to follow up to see if pituitary macroadenoma had responded to levothyroxine supplementation.Pituitary enlargement (pseudotumor of the pituitary gland) is a rare complication of primary hypothyroidism. Early diagnosis and treatment are critical for children with severe primary hypothyroidism to maintain their final height, as late diagnosis nearly always leads to a decline in adult stature. Pituitary macroadenoma secondary to severe hypothyroidism does not need risky and expensive surgical intervention. Because PHPH is rare in children, more credible information is needed to have a better knowledge of how the disease progresses and to develop scientific diagnostic criteria.