Normal Variance in Hormonal Levels: The patient's hormone levels (TSH: 0.53, FSH: 3.78, LH: 3.38, prolactin: 7.1) are within normal limits, and the presence of a copper IUD could be contributing to her symptoms, which might not necessarily indicate perimenopause at her age.

Copper IUD Side Effects: The copper IUD can cause changes in menstrual bleeding patterns, which might be mistaken for perimenopausal symptoms. The patient's denial of pregnancy (with a negative beta hCG) supports the possibility that her symptoms are related to the IUD.
Stress or Other Non-Hormonal Causes: Stress, lifestyle changes, or other non-hormonal factors could be contributing to her symptoms, which might mimic those of perimenopause.

Pituitary or Thyroid Pathology: Although the patient's prolactin and TSH levels are within normal limits, it's crucial to rule out any pituitary or thyroid issues that could cause similar symptoms. A slight deviation in these hormone levels could indicate an underlying problem.
Premature Ovarian Failure (POF): Although less common, POF (now more commonly referred to as premature ovarian insufficiency) could present with similar symptoms and should be considered, especially if there's a significant change in menstrual patterns or if other signs of ovarian failure are present.

Polycystic Ovary Syndrome (PCOS): While PCOS typically presents at a younger age, it's possible for symptoms to become more apparent or to be diagnosed later in life. The patient's FSH and LH levels are within normal limits, but other symptoms such as irregular periods, hirsutism, or metabolic issues could suggest PCOS.
Adrenal Disorders: Certain adrenal disorders could mimic the symptoms of perimenopause, although this would be less common and typically associated with other specific signs and symptoms.