Subclinical Hyperthyroidism with T3 Toxicity: This condition is characterized by elevated TSH levels, normal or slightly low T4 levels, and elevated T3 levels. The high T3 level can indicate that the body is converting T4 to T3 more efficiently than usual, or there could be an issue with the feedback mechanism regulating thyroid hormone production.

T3 Thyrotoxicosis: A condition where there is an excess of T3, which can be due to various causes including Graves' disease, thyroiditis, or excessive ingestion of T3. The normal T4 level with high T3 suggests a preferential secretion or conversion of T4 to T3.
Thyroid Hormone Resistance: A rare condition where the body's tissues are resistant to thyroid hormones, leading to elevated levels of T3 and T4, and high TSH as the body attempts to compensate for the perceived lack of thyroid hormone effect.
Pituitary or Hypothalamic Dysfunction: Abnormalities in the pituitary or hypothalamus can lead to inappropriate secretion of TSH, resulting in abnormal thyroid hormone levels.

Thyroid Storm: Although less likely, thyroid storm is a life-threatening condition that requires immediate attention. It can present with high T3 levels, among other symptoms like fever, tachycardia, and altered mental status.
Pituitary Tumor (TSH-secreting Adenoma): A rare tumor that secretes TSH, leading to hyperthyroidism. It's crucial to diagnose and treat this condition to prevent complications.

Familial Dysalbuminemic Hyperthyroxinemia: A rare genetic condition affecting the binding of T4 to albumin, leading to elevated free T4 levels but normal or low total T4 levels. It might present with normal or slightly altered TSH and T3 levels.
Iodine-induced Thyrotoxicosis: Excessive iodine intake can lead to thyrotoxicosis, especially in individuals with pre-existing thyroid conditions. The presentation can vary, including high T3 levels.