central hypothyroidism 

ENDOCRINOLOGY

A form of hypothyroidism caused by insufficient stimulation by TSH of an otherwise normal thyroid gland, which is often accompanied by multiple other pituitary hormone deficiencies.

Aetiology

• Bexarotene–a retinoid X receptor agonist–therapy

• Growth hormone therapy, which unmasks CH in susceptible individuals

• Hypothalamic-pituitary tumours (pituitary adenomas are the most common cause of central hypothyroidism)

• Lymphocytic hypophysitis

• Molecular causes Defects of TRHR, POU1F1, PROP1, HESX1, SOX3, LHX3, LHX4 and TSHB have been associated with CH

• Babies born to mothers with uncontrolled Graves disease

• Regional radiation therapy

• Subarachnoid hemorrhage

• Traumatic brain injury

• Vascular disease–e.g., Sheehan syndrome

Clinical findings Weakness, fatigue, dry skin, cool extremities, facial, carpal and peripheral oedema, hearing loss, alopecia, paraesthesia, bradycardia, menorrhagia, poor concentration and memory, constipation, carpal tunnel syndrome, weight gain, dyspnoea, hoarse voice

Lab Low free T3 and T4 levels, low or inappropriately normal TSH concentration

Management Levothyroxine; monitor response with serum free T4. 

References http://www.medscape.com/viewarticle/584468

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3114669/