# New-Onset Primary Hypothyroidism in a 14-year-old Girl Presenting as Hemorrhagic Shock From Severe Menorrhagia

## TL;DR

A 14-year-old girl with severe hypothyroidism experienced life-threatening menorrhagia, showing the importance of recognizing thyroid issues in adolescents.

## Contribution

Highlights a rare case linking severe hypothyroidism and menorrhagia in a pediatric patient.

## Key findings

- The patient had profound hypothyroidism with TSH of 423.7 mIU/L and undetectable free thyroxine.
- Autoimmune thyroiditis was confirmed with elevated thyroid antibodies.
- Thyroid hormone replacement and contraception improved the patient's condition.

## Abstract

Hypothyroidism can lead to menstrual irregularities due to its effects on the hypothalamic-pituitary-ovarian axis. Considering this correlation, we present a case of a 14-year-old female in critical condition with hemorrhagic shock from menorrhagia. Initial workup discovered severe anemia with a hemoglobin of 1.8 g/dL (18 g/L) (reference range, 12.0-15.0 g/dL; 120-150 g/L) and profound primary hypothyroidism with a TSH level of 423.7 μU/mL (423.7  mIU/L) (reference range, 0.40-4.2  mIU/mL) and an undetectable free thyroxine of <0.2 ng/dL (<2.5 pmol/L) (reference range, 0.6-1.5 ng/dL; 7.7-19.3 pmol/L). This was confirmed on repeat laboratory testing along with an elevated thyroid peroxidase antibody level of 19.6 IU/mL (reference range, 0.0-9.0 IU/mL) and elevated antithyroglobulin antibody level of 5.0 IU/mL (reference range, 0.0-4.0 IU/mL). She was diagnosed with primary hypothyroidism from autoimmune thyroiditis. Even with blood transfusions, her heavy menstrual bleeding persisted. Thyroid hormone replacement therapy was initiated with oral levothyroxine 50 μg (0.84 μg/kg) once daily, along with high-dose combined oral contraception, with clinical improvement. This severe case presentation illustrates the link between menorrhagia and hypothyroidism in pediatric populations, highlighting the need to address this association in adolescents and ensure optimal care for these patients.